Maybe what we should do is move the Big Issue sellers from Sainsbury's to the narrow bit at the top of Manor Mount.
Wouldn't solve either problem but think of the length of the thread we would have!
But I know this is a serious issue. As others have suggested, I think the real solution is increasing the light phasing at the junction with the South Circ. It seems sometimes this is so short that if the person at the front is a little slow away only 1 or 2 cars get round. The situation is not helped by dozy pedestrians who seem unable to work out that the lights are about to change - it's not really rocket science, if the main road has gone to red Honor Oak Road is about to go to green. I accept that there is a strong argument for pedestrian lights there given the proximity to the museum, but of course that would make things worse....