Roland Perry wrote:

Of course, it depends what you call London. Years ago, I would regularly
drive down the M4 and park at Marble Arch (under Hyde Park), or perhaps
at one of the car parks in the squares north of Oxford Street. There was
never very much of a problem, traffic-wise, and as the nearest sensible
railway station to my home in rural Oxfordshire was more than halfway
into London (at the edge of the Metropolitan), a lot of the time it just
felt "right" to carry on, having got that far.

What part of rural Oxfordshire was that? I can think of parts of it that
it would've been more practical to drive via the M40 than take the
train, but none where the M4 would've been better.