Barry Salter wrote:

2004 'improvements' to the Great Cambridge Junction."

Said 'improvements' comprised:

+ Banning the left turn from Silver Street onto the A406 Eastbound,
meaning traffic either has to travel the entire length of Silver
Street or go all the way round the roundabout, which results in a
significant number of drivers making an illegal left turn, often
straight in front of a bus.

I don't see how you can say banning cars from doing a left turn in front of
a bus causes them to do an illegal left turn in front of a bus. Anyway, are
you sure that banned left turn doesn't date from the construction of the
underpass? Its purpose is surely to prevent traffic from the A10 s/b to the
A406 e/b from cutting through Kendal Parade, which is a reasonably noble
cause.