interesting pictures of the high speed launch HSL 102.
Last month I saw another historic looking craft also with the number 102, as can be seen above. Having done a quick Google I can see it is a historic craft too, one that served in WW2.
The 100 + a bit number indicates a prototype, in this case built by Vosper Ltd, and MTB stands for motor torpedo boat (check out the tubes on the foredeck).
She was the fastest wartime British naval vessel in service at 48 knots, though here keeping to the 6 knot speed limit as part of the ADLS Vets Cruise on Thames.
More information from Wikipedia here or the trust web site here.