This is the big one, following the eastern side of the country from Dover to John O'Groats... and beyond.
It's the only NCN route over 1000 miles long, and forms the UK leg of the North Sea Cycle Route. It's all fully signposted, apart from a short missing section after Whitby.
Most is on-road, a fact that causes some consternation to European cycle tourists arriving by ferry and expecting to see miles of cycle path: no such luck. That said, there are significant traffic-free sections, such as the Lee Navigation towpath that speeds you out of London, and much of the route around Newcastle.
It’s not strictly a coastal route: it often takes long diversions inland, such as at Norwich and Lincoln. South of Yorkshire, the route is generally flat or undulating at most. There are a few hills around Whitby (in the missing section), but the longest climb comes on the inland route from Berwick-upon-Tweed to Edinburgh.
A full tour would take most cyclists a month.