Brent Knoll Camp Brent Knoll Camp is an Iron Age Hill fort at Brent Knoll , from Burnham - on - Sea , Somerset , England . It has been designated as a Scheduled Ancient Monument ( No : 24001 ) , and is now in the care of the National Trust . The hill is high dominates the low surrounding landscape of the Somerset Levels and is visible from the M5 motorway . Name . The word ' knoll ' usually means a small hill or hill - top . The origin of the name Brent is unclear , but one possibility is from a word meaning " burnt " in Old English , suggesting that the settlement was at some time burnt by the Danes . Another proposal is that the name comes from a Celtic term meaning " high place " , or even from another Celtic word , " briant " , meaning law , as the law was anciently promulgated from high places . Another possibility is that the name of Brent simply derives from the local river , the Brent , which gives its name to a Somerset hundred . Brent Knoll Hill . The hill consists of clays and limestone from the Jurassic era and geologically forms an outcrop of the nearby Mendip Hills . Before the Somerset Levels were drained , Brent Knoll was an island , known as the Isle ( or Mount ) of Frogs , that provided a safe haven from the water and marshes . It temporarily became an island again during the Bristol Channel floods of 1607 . There is a small reservoir on the south east flank of the knoll . History . Background . Hill forts developed in the Late Bronze and Early Iron Age , roughly the start of the first millennium BC . The reason for their emergence in Britain , and their purpose , has been a subject of debate . It has been argued that they could have been military sites constructed in response to invasion from continental Europe , sites built by invaders , or a military reaction to social tensions caused by an increasing population and consequent pressure on agriculture . The dominant view since the 1960s has been that the increasing use of iron led to social changes in Britain . Deposits of iron ore were located in different places to the tin and copper ore necessary to make bronze , and as a result trading patterns shifted and the old elites lost their economic and social status . Power passed into the hands of a new group of people . Archaeologist Barry Cunliffe believes that population increase still played a role and has stated " [ the forts ] provided defensive possibilities for the community at those times when the stress [ of an increasing population ] burst out into open warfare . But I wouldn ' t see them as having been built because there was a state of war . They would be functional as defensive strongholds when there were tensions and undoubtedly some of them were attacked and destroyed , but this was not the only , or even the most significant , factor in their construction " . Bronze and Iron Ages . Brent Knoll has seen human settlement since at least the Bronze Age , becoming an Iron Age Fort about 2 , 000BC , which covers an area of . It is defended by a single wall around high and by a single ditch , with an entrance on the eastern side , with a second bank on the north east side . It is surrounded by multiple ramparts ( " multivallate " ) following the contours of the hill , however these have been heavily damaged by cattle and quarrying . Roman . The Romans used its summit as a fortification . An urn containing coins of the Roman Emperors Trajan and Severus was found at the site before 1790 . Other finds have included pennant sandstone roof tiles and painted wall plaster , indicative of a substantial building that is more likely to have been a temple than a villa . Many of the finds are in the Somerset County and Weston - super - Mare Museum s , with Romano - British pottery in the Blake Museum , Bridgwater . Anglo - Saxon . The fort has been claimed as the site of Mons Badonicus . This was a battle between a force of Britons and an Anglo - Saxon army , probably sometime between 490 and 517 AD . Though it is believed to have been a major political and military event , there is no certainty about its date or place . It is also believed to be the site of a battle in 875 at which forces of the Anglo - Saxon kingdom of Wessex drove away the Great Heathen Army led by Guthrum , prior to the Treaty of Wedmore , which was signed three years later . Medieval . During the medieval era the local land was held by Glastonbury Abbey until the dissolution of the monasteries in 1536 . Around the sides and top of the hill are several scarps which may be medieval strip lynchet s . Modern era . Limestone was quarried from the knoll , possibly during the 19th century but the exact date is unknown . During World War II it was the site of a gun emplacement manned by the Home Guard . The remains of slit trenches with angle - iron stakes can still be seen on the western and south - western sides . In 1979 the freehold of was acquired by the National Trust from R P P Johnston . The stone marker on the hill , which also serves as a Triangulation station , commemorates the golden jubilee of Queen Victoria . In 2006 a resistivity survey was undertaken at the northern end of the hillfort . It showed several linear features that might be structures . Legend . According to legend , Ider son of Nuth , who was one of King Arthur ' s knights , came to the Mount of Frogs on a quest to slay three giants who lived there .