The A239, a short road in south London, is probably the shortest A-road to have two detached sections, plus a branch and a secret section!
Route: Mitcham Common – Morden Park
The A239 starts on Mitcham Common, near Mitcham Junction station on the A237. It proceeds northwestwards along Cranmer Road over a railway bridge and continues across the common to a mini-roundabout where it meets Madeira Road, a branch of the A239 which runs eastwards across the common, past the Canons sports centre to a traffic-light-controlled junction with the A236. Cranmer Road continues northwestwards past St Peter's and St Paul's Church, a war memorial, and the famous Mitcham Cricket Club ground to London Road. Here the cricket ground is on the right and the pavilion on the left with players needing to cross the A239 to access the pitch. Something probably unique in cricket! Mitcham cricket club is among the oldest in the world. The total length of the A239 to this point including the branch is about 1 mile.
The road then turns left onto London Road and multiplexes with the dual carriageway A217 as far as Mitcham Station, where there is a crossroads with Morden Road and the unclassified Tramway Path. Mitcham station is now a tram station on Croydon Tramlink but "Tramway Path" has much older roots. Prior to Croydon Tramlink the line was a "heavy" rail line from West Croydon to Wimbledon, but even this was its second incarnation, for the route to Mitcham Junction originally opened in 1803 as the horse-drawn Surrey Iron Railway, a plateway tramroad running from Wandsworth to Croydon. Mitcham Station has an arguable claim to be the oldest still-open railway station in the world. The modern tramway crosses under the A217 (where the two tracks are interlaced owing to the narrowness of the bridge), whereas the ancient tramway apparently had a level crossing.
From Mitcham Station, the A239 leaves the A217 and runs along Morden Road, winding its way past an industrial area and around the edge of Morden Hall Park, a historic former country estate now marooned in London and owned by the National Trust, for about a kilometre, before crossing the River Wandle and reaching the A297 roundabout, south of Morden. The A239 then continues for just under a mile along Central Road, southwesterly to Lower Morden where, after meeting the B278 and turning right, it ends at a set of traffic lights on the A24, opposite Morden Park.
Although still marked on maps as the A239, Central Road has not been signposted as such for over thirty years in the author's recollection.
The A239 number was originally reserved for the Kingston bypass, but this opened as the A3. The road number then lay dormant until about 1930, when it was decided that it should be allocated to three separate Class II roads in the Mitcham area, thus giving the A239 its current route consisting two disconnected sections, one with a spur. As such, it took over the B273 Cranmer Road and B274 Madeira Road in Mitcham as well as the B275 which comprised Morden Road and Central Road, connecting the A217 to the A24 in Morden.