At the south end of Garnault Place is a short bit of road which is signed
"No entry except local buses" on both sides. There don't seem to be any
routes going through it now, and its location makes it unlikely that routes
would ever have gone through it. Why is it there - does it perhaps predate
the barrier in Gloucester Way?

Both left turns from Rosebery Ave into Tysoe St are banned, and I can't see
the point of either ban. Banned left turns are usually to enable a
pedestrian phase at busy lights, but this junction is unsignalled.
Occasionally left turns are banned to prevent rat-running, but both of these
left turns take you towards places that you could have reached more quickly
by taking the previous left turn. Signs say that the banned left turn is
monitored by camera - they're going to a lot of effort to stop people doing
something that is both harmless and pointless.