In 2019, Dover handled 23.4 million tonnes of freight, compared with Felixstowe's 25.3 million tonnes. Here's a scene from FXT:
a) the border processes for both sets of freight will soon be essentially the same, and
b) the change in emphasis from 'process it inland' (Chas) to 'process it nearby' (Gnat)
I suppose it's a good job that our ferries only carry around 180 lorries apiece.