A bit harder than some of the recent puzzles. CF sure does like his canals, and I found myself lost among a plethora of waterways but finally managed to pin it down with the help of the Roman fort reference.
By the way, a certain someone who regularly posts the answer to this competition has the navigation hugely wrong
Initially, I found it easier to identify the canal that opened in 1777. It was nice to see that the lengths of the two featured tunnels were confirmed to the yard in each case!. Reasonably straightforward after that. The swimmer's achievements are quite remarkable. In those days the woollen costumes they wore gained about 5lbs on contact with water!
I have been out all day and not seen any other posts on this week's puzzle.
That is a lovely cheese - Wallace and Gromit's fave!! The one I refer to is not produced in the place that it is named after albeit it is produced from a single day's milk.