The Romans began their occupation of Britain in 45AD, and Watling St was probably their first road, giving them access to the centre of the new Province from the coast at Dover (Dubris).

Marble Arch in London marks the start of the modem A5 trunk road to Holyhead. For most of its way this road follows the Roman Watling Street and also the first trunk road built in Britain after the Romans left: Telford's road to Holyhead, providing a link to the capital for MPs and others from Ireland.

Marble Arch to St Albans

Whilst Telford’s road leaves London from the General Post Office via Islington, the A5 is the Edgware Road from Marble Arch up through Kilburn. This is also Watling Street, a road which starts in Dover and runs in a straight line to London, fording the Thames where the Romans later built the first London Bridge, then turning north via Verulamium to Wroxeter and then probably into Wales.