Both points are on the Metropolitan Line meaning easy access to start and finish - it also goes past Chorleywood giving you a get out early clause. My route (including some small diverts for photos) can be found on Strava .
The walk, which is about 11 miles, follows the route of the River Chess from Chesham to Rickmansworth where it flows into the River Colne. From Chesham Station its a quick stride down to Red Lion St where you see the beginnings of the River at Meades Water Gardens. Here you are next to the water and the area is very pleasant. When you walk through Chesham Moor the woods creep up around you and the river comes and goes from sight.
It's not long before the walk opens up into the countryside and you are walking through farm fields. At Frith Wood there are a couple of routes to take - I took the higher route whereas there is another lower trail - both are marked. My route takes you past the Mary Magdalene Church whereas the other does not. All routes come together at Stony Lane.
At these points you rarely see the Chess - it is hidden from view or on another side of a fence - which is a shame as you don't feel part of it. At Baldwins Wood you have an opportunity to leave the trail to go to Faunden via another public footpath. Soon you will arrive at the M25 - and walk over it on the side of Solebridge Lane. And here is my least favourite part of the walk - you are trapped between 2 high fences for nearly 1km - very dull and loud as one fence is a partition for the motorway.
When you break out of that situation it is not long before you are back in a very protected walkway again - these parts of the walk can be a bit tedious. However, when the landscape opens out again and you are close to the river it does make it all worth it.
The last part of the walk is a nice open park where you are right up against the river - more walkers of dogs and indeed children will be found in this area - you are approaching Rickmansworth.
In all a good walk - not many hills - one main one really. No refreshments on route although there is a pub in Chesham called the Pheasant. If you do the walk starting at Rickmansworth you'll get the pub at the end and also the best open landscapes - in my opinion.
notes - these routes are signposted but please use a map and if you are using a GPS device please make sure you take spare batteries or a charger.
Early exit - at the M25 you can exit down to Chorleywood Station down Solebridge Lane and Chorleywood Common.