Mmm - well looking again at " consultation " doc ,I see that this stretch of Barry Rd marked yellow is described as " existing 20 mph zone road ". So I guess the answer will be ( when I ask Southwark ) that it's inside a 20mph zone - ie adjacent roads are 20mph restricted and signed. Gives the impression that this stretch is also restricted though - and I still can't see any speed restriction signs ,only " you're entering a residential area ,please drive carefully ".