In 1939 was the fastest ship in the RN - and we had a massive navy then, saw her last year at Sandwich altho' flying the Red Duster now. When I was on Defiance in '52 we had 3 MTBs as tenders (not 102) and also 2 midget submarines - went aboard one of the MTBs but didn't get a trip. Got a feeling she has not the original engines - can you imagine the petrol bill?
originally 3 x 1100 HP petrols
Now 2 x600 HP Cummins Diesels
Long bulge on the foredeck shows that torpedo designed to be fired from the stem through a hatch in the bow, although trials showed that the twin tube technique was bettter and she was converted to that format with 2 x 21inch tubes.
Departed Teddington about 0845 08MAy and passed through the lock and pulled up (for breakfast according to the lockie) on the lock layby. Greeted at Shepperton Lock by Walton Bridge Cruiser Club Members 'Jeverek' and 'Lady Greybrooke'. Passed through Shepperton Lock (alone in the lock) around 1130. Narrowboat owner coming out of Shepperton Lock and faced with an MTB got a bit of a shock
Don't need one as a visitor, you just have to swear that the vessel complies with regulations; not sure if you have to show third party insurance either.