Need help, South London Road Knowledge

Not if you use the bike lanes either side of the toll gates.

Unlike the lad on The London Classic a few years ago who comedy clotheslined himself on it while descending and snapped it in half, he got grief and mirth rolled into one.

5k is a bloody long way in S London.

Sydenham/Kirkdale/Wells Park Rd/Taylor's lane/Longton Ave gets you to about 2.5k with a ramp at the end. It would need one marshal on the right turn but I wouldn't really expect any conflicting traffic.

You wouldn't need many laps of Westwood park / Canonbie up then down / back to Westwood park before people agree that they've done 5k and ask if they can stop.

If it's a Sunday, I think your best bet might be the quiet roads in the Docklands. Then cross the tunnel to do the hill climb at Greenwich.

Belmont Hill/ Lee Terrace?

Streatham Common South for the hill climb?

Could come out the other side of the common up by the rookery then drop into hill house road and from that be along valley rd then up valley field rd along bits of leigham court road off towards royal circus then down knollys rd avoiding the lights, leigham vale turn before the lights at palace rd, hillside rd, around a bit to mount nod rd. Coniffer gardens, gracefield gardens, leithcote gardens, sunnyhill rd back to valley rd and then do the start bit in reverse.

College Road is totally unsuitable, checked it out before 5th Floor Track Day.
:(