AndreaC wrote:

However, I seem to recall that once, a long time ago, in the vague
mists of time I tried to change or possibly even exit at Green Park and
it was a flipping horrible station to navigate.

First rule of using the tube ... never, ever change at Green Park
unless you really, really have to.

A friend of mine says knowing this is his test as to whether someone is
a Londoner or not.

D.