The Northamptonshire historian John Morton, writing in 1712, says that an earthwork in his own county was possibly raised as a boundary, like ‘that call’d Rech Dike or Devil’s Dike’, of the Mercians and East Angles’. This great linear earthwork at Reach Fen, on the border of the county, between the town of Newmarket (in Suffolk) and the racecourse, is one of a series of earthworks that cut across the prehistoric highway and later Roman road known as the Icknield Way. Three of them, Devil’s Dyke, Fleam Dyke and Brent Ditch, have their ditch on the north-east side, implying that they were intended to interrupt the advance of an enemy from the South-west. In the past 50 years, their supposed date of construction has ranged from the pre-Roman Iron Age to the mid 7th century CE., but they are in part post-Roman and most frequently explains, as they were by Morton, as frontiers, built by the East Angles against their Middle Anglian neighbors in the 7th or 8th century.
A more colourful hypothesis is that they are defences built by Anglo-Saxon invaders forces to abandon the Upper Thames valley after being defeated by the British, and to fall back step by step on an area protected on the one side by the Fens, on the other by the sea. This setback, it has been suggested, might have been occasioned by the battle of Mons Badonicus (Mount Badon), fought by King Arthur. This was said to have been followed by a long period of peace, and, if it took place at all, was fought around the year 516.
The Devil’s Dyke itself runs from Reach Fen to the woodlands near Wood Ditton. It once ran right through the village of Reach but was cut through between 1743 and 1768. It is still of massive proportions 0 the sort of earthwork one might have expected the Anglo-Saxons to have attributed to Woden as they did as Wansdyke, Wiltshire. In fact they called it simply ‘the ditch’, and this habit persisted into the middle ages, although by then people were also branching out into ‘the Great Ditch’, ‘Mickle Ditch and ‘Reach Dyke’.
In the mid 14th century, it appears under the name St Edmund’s Ditch, because it formed the boundary of the Liberty of St Edmund. According to tradition, the dyke was constructed by the Danish king Canute, who, to make amends for his father Sweyn Forkbeard’s rough treatment of the monks of Bury St Edmunds in Suffolk, granted them privileges that ran as far as this ditch/
The earthwork’s present name does not appear in records until 1574, in the Laton from Daemonis fossam, to which Camdem in 1594 gives the English equivalent, Devil’s Dike. The Latin author says it was so-called because it was popularly thought o have been built by the art of the Devil; but Camden explains it as a corruption of the name of a man called Davilier, who held the manor of Broome in Suffolk by the feudal service of marshalling the ‘footmen’ of Norfolk and Suffolk, whose point of assembly was at this ditch. BOTH explanations may be correct, the name Davilier suggesting to the locals the old tradition of the Devil as builder.