High Quality Content by WIKIPEDIA articles! The A40 is a major trunk road connecting London to Fishguard, Wales. Starting from the City, the A40 in London is an A road passing through seven London Boroughs: the City of London, Camden, Westminster, Kensington & Chelsea, Hammersmith & Fulham, Ealing and Hillingdon, to Junction 1 of the M40 motorway in Denham, Buckinghamshire.