I've often been held up in a two lane jam all the way up the hill to the
M40 from the Marlow junction. The OP should consider other ways to get
from Marlow to the M40, if possible! It might even be quicker to go down
to the M4 and east as far as J3, then north through Yeading and
Northolt.

Why? That's absolute lunacy.

Using "main" roads it would almost certainly reduce the journey time.

Would it? When you say through Yeading and Northolt I'm guessing you're
talking the A312, and not the old main road (Yeading Lane?). I certainly
wouldn't choose to go that way in the rush hour, having experienced queues
up to the White Hart roundabout to a small extent and, to a much larger
extent, up to the Target roundabout, with that peak hours bus lane taking
out half of the road capacity when it's needed most!

Or were you thinking about heading up past South Ruislip station and in to
Harrow that way?

The road up past Marlow Bottom (Wycombe Road)
is a very easy and hassle-free way to get up to Handy Cross.

Sounds fine, I've not tried that rat run, but thanks for alerting me to
it - I will next time I'm there!

Keep it quiet though, you don't want it getting all over the internet, or
the route will quickly clog up. :-)

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