The Magna Carta Project

Original Latin


Omnes kydelli de cetero deponantur penitus de Thamisia, et de Medewaye, et per totam Angliam, nisi per costeram maris.


All fish-weirs are in future to be entirely removed from the Thames and the Medway, and throughout the whole of England, except on the sea-coast.

Audio commentary

Commentary for general audience

Clause 33 is unusual, in that it demanded action to remedy an abuse apparently unconnected with the actions of the king or his agents.  Mainly intended to benefit the city of London, it was extended to cover the whole of England, in ordering the removal of fish-weirs from rivers  In the form complained of, they had probably been relatively recently introduced from the Continent.  Substantial V-shaped structures of wood and sometimes stone, which were set in riverbeds to catch fish by guiding them into central baskets or nets, they proliferated in the Thames, where they helped to provide food for London’s growing population, and also to meet the needs of the devout who ate fish instead of meat on the numerous religious fast-days.  But they also constituted serious obstructions to river craft, and hence to trade, both upstream and downstream of the city, and presumably hindered navigation on other rivers as well.  The explicit exclusion of coastal weirs from Clause 33 was no doubt principally due to their being usually less likely to obstruct shipping than riverine ones, but it may also reflect the fact that secular and ecclesiastical magnates were the likeliest owners of such devices along the shores.

Commentary for secondary school students

Most of the clauses of Magna Carta aimed to remedy abuses committed by the king and his agents.  Clause 33 is an exception, in that it demanded that the king use his powers for the benefit of his subjects, or at any rate a particular group of them, without suggesting that he was himself responsible for the grievance in question.  Indeed, both Richard I and John himself had already tried to resolve what proved to be a recurring problem.  The problem was the fish-weir, which was proliferating in the Thames, and probably in other rivers as well, to such an extent that it was becoming a serious hindrance to navigation, and so to trade.  There had been traps to catch fish in English waters for centuries, but a new form seems to have been introduced from the Continent in the late twelfth century, larger and heavier than its predecessors.  Made of poles and beams, and sometimes with a stone base, it was a substantial V-shaped structure, which worked by guiding fish that swam into its arms towards a net or basket at its centre.  London needed fish, both to feed its growing population and to meet the needs of those who observed the numerous fast-days of the Church by eating fish instead of meat.  But it needed to keep its waters clear as well, so that shipping could move safely up and down the Thames, and the new fish-traps clearly proved a serious obstacle.  The total removal of fish-weirs, from the Thames and Medway (downstream from London, on the northern shore of Kent), and also from all other rivers, was ordered in response.  A concluding phrase, excepting coastal fish-weirs from the prohibition, was probably added in recognition that such devices were less likely to hinder the movement of boats than weirs in rivers, but it may also have been intended to benefit the ecclesiastical and secular lords who were the likeliest owners of fish-traps which were set up along the shoreline.

Commentary for academic researchers

(a) The problem of the fish-weir

Clause 33 appears in the same context in Magna Carta as its equivalent clause, number 23, does among the Articles of the Barons.  In both it is preceded by stipulations about the property of convicted felons, and followed by the prohibition of the writ Precipe.  It differs from these, and from most of the other clauses in the Charter, however, in that it was seemingly not intended to rectify oppressive or extortionate behaviour on the part of the king or his officers – there is no suggestion in the Charter, or anywhere else, that John and his agents had been filling English rivers with obstructions.  Rather it demanded the exercise of the royal prerogative in ways advantageous to the king’s subjects, and in particular to the city of London, which was its principal (though not its sole) beneficiary.  Clause 13 of Magna Carta gave the capital a sweeping confirmation of its ancient liberties, but its citizens wanted specific concessions as well.  Probably earlier in 1215 they drew up a series of demands, apparently for presentment to the king (possibly it was intended to be laid before the barons as well), of which the first declared `Concerning the Thames, that it should be absolutely and wholly the city’s’.1  It seems highly likely that Clause 33 originated in this requirement, with its very generalised terms being both made more precise and given a wider application.

The word translated here as `fish-weir’, kidellus, was a Latinised form of the Old French quidel.2  First recorded in Normandy in 1180, among the issues of Caen,3 it defined a large V-shaped weir made of rows of upright poles, connected by transverse rods or beams, which were themselves interwoven with brushwood or withies.4  The poles were either sunk directly into the bed of the sea or river or set into low stone walls; the latter were often used for coastal weirs, which could be substantial structures.  The two lines of poles did not meet, but were separated by a gap which was filled by a net, or more often, a wickerwork basket.with a hole at one end.  Fish entering the weir would be guided by its walls into the centre and then into the basket; a collar of inward-facing sticks at the point of entry acted as a valve to prevent their swimming out again.  A weir could be laid out facing in either direction, but it was most commonly placed with its apex facing out to sea or downstream.  A coastal weir would capture fish which, having come close to the shore to feed in the shallows, then tried to swim back out to sea, while a riverine one, though it could be positioned with its mouth facing downstream, to catch salmon coming upriver to spawn, was more likely to face the other way, so as to ensnare eels and other fish as they moved towards the sea, either with the current or, in estuaries, with the outgoing tide.

(b) The interest of London

An assured supply of fish was essential in an age when religious observance could lead to devout laymen abstaining from meat for between a third and a half of the days in the year,5 and when meat was unaffordable for many men and women, whether they were devout or not.  The Thames, described as `so full of fish’ by William FitzStephen, who also eulogised the city’s cookshops in which fish both large and small could be bought,6 was a vital element in the provisioning of London – the fish referred to in regulations for the city’s fishmongers from later in the thirteenth century included mullets, whitings, sprats, mackerel, rays, congers, dories, turbot, dabs, whelks, porpoises, oysters, salmon, cod, haddock, herrings, eels, mussels and sturgeon,7 and though not all of these will have been caught in the Thames, comparisons with the records of later epochs suggest that many of them could have been.  The right to catch fish in the river may have been disputed, or at any rate uncertain.  An inquest probably held in the reign of Henry II found that in the time of King Stephen a `liberty of the River Thames’ had stretched from Staines to Baynard’s Castle, with its fishing being controlled by the latter’s lord.8  Below Baynard’s Castle, which stood at London’s south-west corner, the fishing was presumably already controlled by the city, whose governance extended as far downstream as a line from Crowstone, between Leigh-on-Sea and Southend-on-Sea on the north side of the estuary, to Yantlet Creek on the Isle of Grain.9  Only in 1237 was it extended as far upstream as Staines as well,10 but from the fact that Magna Carta made no reservation of the rights of the lord of Baynard’s Castle, even though in 1215 he was no less a man than the baronial leader Robert FitzWalter, suggests that either Robert was prepared to make a tacit surrender of this element in his lordship in order to retain London’s support, or that he was no less tacitly acknowledging that his rights in the Thames were effectively obsolete.

In the twelfth-century inquest into the liberty of the Thames fish were described as having being taken in the lordship of Baynard’s Castle by men using seine-nets, which had floats at the top and weights at the bottom, and were cast from the bank – a number of them were said to have been taken by force and burnt in the house of `the keeper of the waters’.  Although fish-weirs had long been known in England (impressive remains, dating from well before the Norman Conquest, have been excavated in the Blackwater estuary, off the Essex coast),11 it seems likely that in their earliest forms they were insufficiently robust for the tidal waters of the Thames estuary, which in the middle ages rose much higher, and ebbed and flowed much faster, than they do today.12  Judging by its relatively late appearance in the written record, the kidellus, though similar in design to its forerunners, was probably an innovation of the second half of the twelfth century, originating in northern France or the Low Countries and soon brought across the Channel to London.  It may not have been fortuitous that its arrival on the Thames seems to have coincided with that of the tidal mill, which also needed to be very strongly made to survive the buffetings of the river – one datable to 1194 which has been excavated at Greenwich was found to have been a huge timber structure resting on chalk cobbles and great squared oak piles, and like the kidellus may have been continental in origin or inspiration, since it stood on land owned by St Peter’s abbey in Ghent.13

The installation of large and strongly-built fish-weirs in the Thames no doubt made a useful contribution to keeping London supplied with food, but it quickly also created severe problems for the navigation of the river.  That these were at first seen primarily in a military context is suggested by the fact that the power to license fish-weirs was initially exercised by the constable of the Tower, who received a yearly payment for them.14  Substantial works were carried out at the Tower in 1190 and 1191,15 and it would have been important to keep the river clear so that supplies of stone (much Purbeck marble was used) and timber could be brought there safely.  But the weirs must have been no less of a hazard to trading vessels, and since London played an important role in providing supplies for Richard I’s campaigns in Normandy in the late 1190s, civic and royal interests could be seen to coincide, or at any rate presented as coinciding.  Accordingly on 14 July 1197 Richard granted the city a charter which ordered the removal of all the weirs in the Thames, and annulled the rights over them of the constable of the Tower,16 in the process describing the weirs as detrimental not only to the city but also to the whole realm.  The charter says nothing, however, to suggest who in the years on either side of 1200 was responsible for making and maintaining these forbidden devices, and other sources are equally silent.  It is possible that then, as later, London fishmongers were among the offenders, but evidence is lacking.17

Richard I’s charter seems to have had limited effect, for on 17 June 1199 King John granted the Londoners a further charter, again ordering the removal of all fish-weirs, and extending the prohibition to the Medway as well as the Thames; anyone who constructed a weir in either river in future would be liable to a £10 amercement.18  Probably the prohibition was seen as unlikely to be effective unless it was extended downstream, but it is also possible that Richard’s charter had caused some of those affected by it to move their weirs into Kentish waters, which may already have been as assiduously fished as they were to be in later centuries.19  But John’s charter, like its predecessor, clearly failed to keep the Thames clear for ships.  In 1237 the Londoners claimed that the people responsible for fish-weirs had been excommunicated, at an unrecorded date which can have been no later than 1205, by Archbishop Hubert Walter and all the bishops of England, and that this sentence had later been renewed by Archbishop Langton, again with the backing of the other bishops.20  If the claim was true, the deployment of spiritual sanctions underlines the seriousness with which the offence in question might be taken, even though they, too, proved ineffective in keeping the river clear; on the evidence of their subsequent demands, the Londoners came to believe that this could only be achieved if they had the control of the whole of the Thames.  The Charter did not make this sweeping concession, but repeated John’s prohibition, without a penalty clause, and extended it to all English rivers.

(c) Other rivers

Although that extension may have been no more than an acknowledgement of a recent proliferation of fish-weirs in English rivers, it seems likely that it was also specifically intended to benefit London, which had an interest in keeping the Thames free of obstructions for many miles upstream, and also in ensuring that its tributaries could flow unhampered into the main river.21  As the city and its population grew, so the hinterland upon which it drew for its food supplies grew also.  Charters licensing the owners of boats to carry goods free of tolls (from which the Londoners had been exempted since at least 1135) between London and Abingdon and between London and Oxford, issued in 1204 and 1205 respectively,22 illustrate the potential of a considerable length of the Thames for transporting merchandise at this time, just as a similar charter for the countess of Leicester in 1207, granting her the same exemption for her boats at Ware, on the River Lea – the principal tributary of the Thames, which it joins on the eastern side of the Isle of Dogs – shows how waters flowing down to the estuary might be used for carrying supplies in the direction of the capital.23  In all these cases, a blockage of the river, whether it was the Thames or a tributary, by a fish-weir would have been something to be avoided.  The same must have been true of other waterways, for instance the River Itchen in Hampshire, linking Winchester to Southampton, which was recorded in 1205 as having been obstructed by an undefined `encroachment or impediment’.24  Indeed, although the extent to which waterways were used to carry goods has been the subject of some controversy, the very fact that Clause 33 applied to the whole of England suggests that river transport was perceived as likely to be of widespread importance, perhaps especially for the movement of bulky commodities like grain.25

The exclusion of coastal weirs from Clause 33’s otherwise blanket prohibition was new to Magna Carta.  Exactly what was meant by per costeram maris is not in fact entirely clear, since a phrase so broad could in principle have applied to the entire English coastline, but presumably did not do so.  Probably the deciding factor was the depth of the water.  There was manifestly no attempt to prevent the construction of weirs along the shores of the Severn estuary, where they proliferated for centuries – a number of them have been excavated at Sudbrook Point, south of Chepstow, datable to both before and after 121526 – most likely because the estuary was broad enough, and deep enough at its centre, to allow navigation past the weirs in the direction of Gloucester.  The available technology was probably not capable of placing weirs in the entrances of ports which opened into deep waters.  Coastal weirs were sited in shallow waters, where they could be set up without difficulty and where there was easy access to the traps holding such fish as they caught.  Their size and complexity, however, made them expensive to build and maintain, so that they were primarily the creations of secular and ecclesiastical lords, who had them constructed (particularly in the case of religious houses) to ensure that they had an adequate supply of fish, and also to provide them with a valuable commodity which could be sold on the open market.27  Coastal weirs were probably excluded from Clause 33 mainly because they were less of a hindrance to navigation than fish-traps in rivers, but the omission may also have owed something to the willingness of the barons to act in their own interest, as well as in that of their London allies, and beyond them of the whole kingdom.  The range of benefits arising from Clause 33 was potentially a wide one.


M. Bateson, `A London municipal collection of the reign of John’, English Historical Review 17 (1902), 480-518, 707-30, at 726.


D. Hooke, `Uses of waterways in Anglo-Saxon England’, J. Blair (ed.), Waterways and canal-building in medieval England (Oxford, 2007), 37-54, at 53, n. 107.


V. Moss (ed.), Pipe rolls of the exchequer of Normandy for the reign of Henry II, 1180 and 1184, Pipe Roll Society, new series 53 (2004), 38.


For information about fish-weirs I have relied particularly upon A. Wheeler, The tidal Thames: the history of a river (1979), 80; C.R. Salisbury, `Primitive British fisheries’, G.L. Good, R.H. Jones, M.W. Ponsford (eds.), Waterfront Archaeology, Council for British Archaeology Research Report 74 (1991), 76-87; A. O’Sullivan, `Place, memory and identity among estuarine fishing communities: interpreting the archaeology of early medieval fish weirs’, World Archaeology 35 (2003), 449-68.


C.M. Woolgar, `”Take this penance now and afterwards the fare will improve”:seafood and late medieval diet’, D.J. Starkey, C. Reid, N. Ashcroft (eds.), England’s sea fisheries: the commercial sea fisheries of England and Wales before 1300 (2000), 36-44, at 36-7. 


D.C. Douglas and G.W. Greenaway (eds.), English Historical Documents ii: 1042-1189 (2nd edn., 1981), 1025-6..


H.T. Riley (ed.), Munimenta Gildhallae Londoniensis i: Liber Albus (Rolls Series, 1859),373-86.


Bateson, `A London municipal collection’, 485-6; C.N.L. Brooke and G. Keir, London 800-1216: the shaping of a city (1975), 214-15.


Wheeler, The tidal Thames, 5.


Bateson, `A London municipal collection’, 485-6.


O’Sullivan, `Place, memory and identity’, 452-4.


D. Goodburn and S. Davis, `Two new Thames tide-mill finds of the 690s and 1190s, and a brief up-date on archaeological evidence for changing medieval tidal levels’, J. Galloway (ed.), Tides and floods: new research on London and the tidal Thames from the middle ages to the twentieth century, Centre for Metropolitan History Working Papers series 4 (2010), 1-13, at 12.


art. cit., 6-10.


W. de G. Birch, The historical charters and constitutional documents of the city of London (revised edition, 1887), 9-10.


R.A. Brown, H.M. Colvin, A.J. Taylor, The history of the king’s works i: the middle ages, 2 vols. (H.M.S.O., 1963), ii, 708-9.


Birch, Historical charters, 9-10.


H.T. Riley (ed.), Munimenta Gildhallae Londoniensis ii:i: Liber custumarum  (Rolls Series, 1860), 40.


ib., 13-14.


G.M. Draper, `Timber and iron: national resources for the late medieval ship-building industry in Kent’, S. Sweetinburgh (ed.), Later medieval Kent, 1220-1540, Kentish history project 9 (Woodbridge, 2010), 55-77.


Riley, Liber custumarum, 42.


R.H.C. Davis, `The ford, the river and the city’, Oxoniensia 38 (1973), 258-67; R.B. Peberdy, `Navigation on the river Thames between London and Oxford in the later middle ages: a reconsideration’, Oxoniensia 61 (1996), 311-40.


T.D. Hardy (ed.), Rotuli Litterarum Patentium, 1201-1216 (Record Commission, 1835), 38, 52.


ib., 69.


T.D. Hardy (ed.), Rotuli Litterarum Clausarum, 1204-1224 (Record Commission, 1833), 52.


See J.F. Edwards and B.P. Hindle, `The transportation system of medieval England and Wales’, Journal of Historical Geography 17 (1991), 123-34; J. Langdon, `Inland water transport in medieval England’, Journal of Historical Geography 19 (1993), 1-11; J.F. Edwards and B.P. Hindle, `Comment: inland water transportation in medieval England’, Journal of Historical Geography 19 (1993), 12-14.


S. Godbold and R.C. Turner, `Medieval fishtraps in the Severn estuary’, Medieval Archaeology 38 (1994), 19-54.


W.R. Childs and M. Kowaleski, `Fishing and fisheries in the middle ages’, Starkey et al., England’s sea fisheries, 19-28, at 25.

Magna Carta 1215
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