High Quality Content by WIKIPEDIA articles! The A1 road in London is the southern part of the A1 road which passes through London from its start at Aldersgate in the City of London to Borehamwood on the northern fringe of Greater London, going on to cross under the M25, briefly becoming the A1(M) motorway before continuing to Edinburgh. The road travels through the City and three London boroughs: Islington, Haringey and Barnet, which include the districts of Islington, Holloway and Highgate, and travels along Upper Street and Holloway Road, crossing the North Circular Road in Barnet.