Roman London was built on the north bank of the Thames, the site of the modern City. The river, roughly in its present position by the time of the Roman conquest, was probably tidal at London, although tides may not have reached as far as Westminster (Milne 1985, 79-86). At high tide the river may have been as much as 1 km across and most of the south bank would have been submerged, although there were important islands of dry land at Westminster and Southwark. At low tide the channel would have shrunk to about 275 m, still considerably wider than the river of today which is about 200 m across. On its north side the Thames had cut against a pair of low hills, and it was here that the town was built. The western hill, Ludgate Hill, is now occupied by St Paul’s Cathedral whilst that to the east (hereinafter referred to as Cornhill) is presently surmounted by Leadenhall market. These hills were separated by the valley of the Walbrook, the upper parts of which remained marshland until reclaimed in the Roman period. To the west of Ludgate Hill was the Fleet river, and on both hills there were springs which fed small streams.
Despite intense search no trace has been found of any immediately pre-Roman occupation in the City, although several sites have produced remains of earlier prehistoric activity, especially in the area of Bishopsgate. The skeleton of a young man found at the Tower of London might have been buried in the late Iron Age but this is far from certain (Parnell 1985, 5-7). The distribution of certain pre-Roman coin types seems to indicate that some form of centre had been established in the lower Thames valley, west of London, in the early first century BC (Kent 1978, 53-8; Haselgrove 1988). There is no evidence, however, that this hypothetical site had continued beyond c. 60 BC and it is of little evident relevance to the later history of the area. We can be reasonably certain that there were no major settlements in or around London at the time of the conquest.
Limited pre-Roman occupation has been noted at both Westminster and Southwark, where the islands of dry ground next to the river had attracted settlement (Merriman 1987, 324). The most interesting evidence