Is it this?
NORWOOD ROAD / CHRISTCHURCH ROAD: Routes 2 68 196 201 322 415 432 468 P13 X68 diverted both ways while the emergency services respond to a road traffic collision. Routes 2 432 northbound via Ernest Avenue, Knights Hill, Crown Lane, Leigham Court Road, Streatham Hill, Christchurch Road and Hardel Rise and southbound via Tulse Hill, Norwood Road, Croxted Road, Thurlow Park Road, Lancaster Avenue and Norwood Road. Routes 196 468 northbound via Beulah Hill, Crown Lane, Leigham Court Road, Streatham Hill, Christchurch Road, Hardel Rise, Tulse Hill and Norwood Road and southbound via Norwood Road, Croxted Road, Thurlow Park Road, Lancaster Avenue and Norwood Road. Route X68 northbound via Beulah Hill, Crown Lane, Leigham Court Road, Streatham Hill, Christchurch Road, Hardel Rise, Tulse Hill and Norwood Road and, while also diverted southbound, misses no bus stops. Route 322 northbound via Gipsy Hill, South Croxted Road, Croxted Road and Norwood Road and southbound via Norwood Road, Thurlow Park Road, Lancaster Avenue and Norwood Road. Route 68 terminates and departs at Herne Hill. Route 201 terminates and departs at Streatham station. Route 415 terminates and departs at Brixton. Route P13 terminates and departs at West Dulwich.
Must've been going on for a while - I saw 432s being turned round ar Morval Road neear the Hootananay at 4.45pm