The A23 road, in its original form, was a major road in the United Kingdom running between London and Brighton, East Sussex. It became an arterial route between these two places following the construction of Westminster Bridge in 1750 and the consequent improvement of roads leading to the bridge south of the river by the Turnpike Trusts. The increase in population of Brighton in the late eighteenth century, which transformed it from a small fishing village to a large seaside resort, enhanced the importance of this route, as did the residence there of George IV, as Prince of Wales, who made Brighton into a place of fashion. Today the original A23 has been bypassed round Croydon; and by the M23 motorway for the section of its route between Hooley and Crawley.
The 53-mile route from London to Brighton forms the basis of the route of the annual London to Brighton Veteran Car Run. This is featured in the film Genevieve although in the film most of the rural motoring scenes were actually shot in Buckinghamshire. The A23 is also used for other various other London to Brighton events.
Main roads running from the centre of London are always deemed to start from Charing Cross, although the A23 itself begins as Westminster Bridge Road near Waterloo station. Almost immediately it turns south; the straightness of much of the heading south belies its Roman origins.
The road becomes:
- Kennington Road: 1 mile (1.6km) in length; near Kennington Park it joins the A3 (Kennington Park Road), but soon bears south again, becoming in turn over the next five miles (8km):
- Brixton Road
- Brixton Hill
- Streatham Hill
- Streatham High Road
- at Norbury the continuing road becomes London Road; after 1.25 miles (2km), at
- Thornton Heath the Croydon Bypass, Thornton Road and then Purley Way (known for its superstores, particularly Ikea, and for the site of the original Croydon Airport) takes the place of the original road through Croydon, which is now the A235, rejoining the "new" A23 at Purley (near the Purley War Memorial Hospital), now named Brighton Road.
- continuing south through Coulsdon on the newly opened Farthing Way, the relief road for Coulsdon Town Centre, over the North Downs to Hooley. the start of the M23 motorway
- through the built-up areas of Merstham; Redhill, Salfords and skirting Horley
- making an end-on connection with the M23 spur for Gatwick Airport the A23 becomes dual carriageway as it is diverted round the airport; it rejoins the original route at Lowfield Heath and continues south into Crawley as London Road
- Crawley Ring Road: the original road was through the town
- Pease Pottage, the southern junction with the M23
- through relatively rural countryside of West Sussex the road runs into Brighton/East Sussex over the South Downs
Major roads intersected by the route