The A22 diverges from the A23 south of London at Purley Cross Junction (south of Purley). It runs over the North Downs into Surrey, crossing the M25 London Orbital Motorway just north of Godstone. This section incorporates the Caterham bypass, which opened in 1939 as one of the earliest such roads in the country, including the Wapses Lodge roundabout at the northern end. It then travels along the route of an ancient Roman road.