The A205 or South Circular Road is a direct route which crosses South London, UK, running from Woolwich in the east to the junction of the A406 (North Circular Road), the M4 and the A4 at Gunnersbury in the west.
Together with the North Circular Road, the South Circular forms a ring road through the inner part of Outer London. This ring road does not make a complete circuit of the city, as the crossing of the River Thames in the east is made on the Woolwich Ferry.
Unlike the North Circular, the South Circular is not a purpose-built route, but a collection of pre-existing suburban roads joined together, which has resulted in a disjointed feel, with totsos at several junctions. This makes it seem little more than a sequence of road signs.
The South Circular Road was first proposed in Sir Patrick Abercrombie's County of London Plan of 1943, as the southern half of one of a number of ring roads around the capital. Abercrombie designated it as the "C Ring" (the third ring out from the city centre); however, the plan for a high-quality road was not realised and the semi-circular route was assigned to existing roads through the southern suburbs; these roads retain their historic names.
The Wikipedia page is [1] and the Lonodn Traffic page is [2]