Colin Rosenstiel wrote:

This would include cyclists or motorcyclists not overtaking other
vehicles on the left where they are turning left, and it also
includes, for example, giving a lorry a wide berth on a roundabout. It
would include not blocking a faster vehicle from overtaking a slower
one. It would include many other courtesies.

I'm not sure where the left turning vehicle is coming from behind, how a
cyclist or anyone else is supposed to do that.

Do what? A considerate bus driver wouldn't turn left onto another
vehicle that was already there. They should be booked if they do.

A considerate cyclist, OTOH, wouldn't overtake a bus on the left if,
for example, it was indicating to turn left but moving slower than the
cyclist. Arguably, it is a poor idea to overtake on the left of any
vehicle. If the bus is at a stop but unable to pull in for whatever
reason, it is particularly stupid - yet I've seen it.

Neil