FYI, The Victor has maxerat brake units, and it is firmly part of Victor technique teaching that you keep heels down and toes away from the brake pedals - the upper part of the rudder pedals - until firmly on the ground and the wheels have spun up. I think I went on the brakes while still on the grass but just before getting back on the tarmac. The puff of white smoke I cannot explain, we did look at the wheel tracks but I thought they were all on the grass - perhaps not though - might have been on the taxyway and then a bounce onto the grass. The main thing though is that the aircraft had a new set of tyres fitted for the event on all but one front bogie - and that was "as new"! As I said earlier, the stbd brakes were hot when we stopped, but there was no apparent tyre wear, and certainly no flat spots on any of the tyres.
You are quite right ...... there was a major "Oh S..." moment as I realised we were flying, and I got the nose down and saw exactly where we were!!
Bob