I am fairly new to the area, so not aware of the history of traffic management.
Unfortunately, the reduction of traffic on one street, often simply diverts the traffic into a neighbouring street to the detriment of a different set of residents.
Decker makes the point (above) in this thread that:
“Having it (Manor Mount) open doesn't solve anything because it just relocates a traffic problem from a main road, to a residential street ….Traffic should be on Honor Oak/London Rd/South Circular.”
But Honor Oak Road is also residential - just as much as Manor Mount – perhaps more residential in that more residents live there as it is a longer road than Manor Mount and with many more dwellings (also an infant school).
One could also argue that Devonshire Road needs traffic reduction more than Manor Mount, Davids Road, and Waldenshaw Road, because it is 100% residential and has more residents than Manor Mount, Davids and Waldenshaw.
I do have some sympathy with some drivers turning into Manor Mount from Honor Oak Road. On a bad day it can take 15 minutes to get through the lights from Honor Oak Road onto the South Circular, and the lawful alternative is an even worse queue on Devonshire Road. If someone is late for something important it is frustrating to be held up, especially if there appears to be no good reason for the 'No Entry' into Manor Mount.
Whichever local politician can come up with a feasible and equitable traffic scheme would have my vote, regardless of their other policies!