I flew the venerable Dominie from 1987-92 and also did my CAA ATPL type tech exams on it. Then, according to UK CAA, it was an HS125 1B-522.
Funny how certain things stick in your mind. At max take off weight (21000 pounds) V speeds were
V1/VR 121
V2 127
Single Eng Climb Spd 172
Max landing weight (17500 pounds) Vat was exactly 120 Kts - hence it just squeezed into Cat B. I never flew the 'Corgi Carrier' variant but I am guessing that it had either a heavier max landing weight (faster Vat) or some other reason to increase the Vat - hence Cat C.
Usual caveats about age, alcohol and incipient senility apply to all of the above.
