In message , at
21:07:12 on Tue, 15 Sep 2020, Arthur Figgis
remarked:
And the number of craft that are based on the Thames that can fit the Canal
Dimensions must be a fairly small percentage. At least as far as I know the
Boat Safety Certificate is now common between
CART and EA managed navigations, one time they differed a bit.

You would only want to do it doing for the sake of doing it but if
you had a suitable craft like an old ships lifeboat conversion and
the navigational skills accompanied by a suitable stomach it may be
possible to go Grand Union , Kennet and Avon ,Bristol Avon then
around the Coast but the type of person who would want to undertake
such an adventure would probably be doing it regardless of the bridge
closure. The specialised sea going barge type one of which
featured the Actor Timothy Spall going around the coast will fit
the Grand Union but is just a little too big for bits of the Kennet and Avon .

How difficult/expensive is "put it on a lorry"? A friend who recently
bought a narrow boat apparently had it delivered by road to a yard
somewhere in west London then sailed it into central London.

If it's too big to fit through the Regents Canal (73ft 4" x 13ft 10"),
it's probably too big to go on the back of a lorry.
--
Roland Perry