It might have been my imagination at the time, but it looked like Peter Davison, the Fifth Doctor, filled out his cricket trousers very nicely.
David Tennant was in his boxers on Friday Night Project tied up on a bed. You could see outline of his dick kinda and it was nice
My best guess is it's a toss-up between David Ten-Inch and Paul McGann.
Sounds like a nice scenario...
Oh, if I can dream..