John Rowland wrote:
Brimstone wrote:

The Hanger Lane underpass long predates the gyratory which sits on
top of it. The underpass is shown on a very early 60s A-Z map of
London.

Was it lengthened when the gyratory was put in? It seems too long to
have been built just to go under a crossroads.

Nope, it is as it has always been. If you look at a plan view of the
gyratory, you'll see that it is to the north of the A40 and its underpass.
Even before the gyratory was built, the junction was a large one.