National Cycle Route 1

From the Wikipedia page, which gives a full listing of the route:

National Cycle Route 1 (or NCR 1) is a route of the National Cycle Network, running from Dover to Shetland.[2][3] The 1,695-mile-long (2,728 km) cycle-path is located in the United Kingdom.

The two relevant sections on the Wikipedia page are Sittingbourne to London and London to Colchester