We cycled from London to Dover, (Via Rochester, Whistable, Deal ), mostly using NCN1, the countries premiere cycle route from the main port to the capital.
There is a section in Gravesend (Gordon Prominade to Wharf road) that I would show you, except even that it's not even on Google view!
The nations main cycle route goes through the arse end of an industrial estate, then goes through a gap in the fence and down a very narrow footpath with a concrete wall on one side with steel fence posts keeping the razorwire in place, I honestly thought we had gone wrong, and it was not a place I would go on my own even in broad daylight.
This section of the route would not be usable by anything out of the ordinary, such as skinny tyres, tandems or recumbents or a night.
A few miles on we met 3 Dutch girls going in the opposite direction. We told them to get the train into London, as the already dreadful cycle route, for them, would only get worse, a lot worse .
Having said which, I was very impressed with the Viking Way cycle route between Whistable and Deal, it was almost European level cycling, one to be repeated.