In message , JNugent
writes

Paul Terry wrote:

If you mean the Chiswick flyover, it wasn't even part of the motorway
when it was built in 1959 by Tory transport minister Ernest Marples'
construction company, Marples Ridgway - it was just a flyover on the
A4.

You must be thinking of a different stretch of road - perhaps the
Hammersmith Flyover (which *is* part of the A4).

No, Richard J has outlined the correct sequence of events, and you will
also find them recorded at

http://www.cbrd.co.uk/motorway/4.shtml

where you will see that the Chiswick flyover opened in 1959. It didn't
become part of the M4 until 1965.

I'm sure the Chiswick Flyover was built in the 1960s (along with what was
then the rest of the M4, as far as Maidenhead).

It was originally going to be designated A4(M) [1] - ie, the motorway
was only going to be a bypass of A4 from Chiswick to Maidenhead), but
it was still a motorway.

The Maidenhead (eastern) bypass was indeed originally numbered A4(M) and
part of it was later incorporated into the M4 (*) - but the intention to
build a motorway from London to South Wales dates back to pre-war road
planning days. It was designated the "South Wales Motorway" at an early
stage, and appears as such in maps even before constructed started (e.g.
the 1961 Bartholomew Reference Atlas of London).

(*) See http://www.free-definition.com/A404M-motorway.html
--
Paul Terry