The Bulldog is unpredictable in the spin and was especially so early on in its history.
As RAF QFI's we were obliged to fly mutual high rotational spin recoveries once a month (or was it every 3 mths?). We used to pre-brief the entry and recovery drills so that the other "safety" pilot did not get left behind the plot, as things used to happen very quickly.
The two usual ways of getting a "high rotation" were either to reverse the rudder without following up with stick forward, or simply to move the stick forward about an inch from fully aft. As elevator loads in the spin were quite high for a light aircraft the latter was easy to get accidentally. For that reason students were taught to use both hands on the stick at entry. This also helped keep the ailerons neutral, which was also required to prevent oscillations / other funny things happening.
The roll acceleration and sustained rates were quite alarming.
Two incidents stick in my mind. One involved a QFI plus student. Student messed up recovery drills, a/c went high rot. QFI could not recover so told student to "Jump, Jump, Jump!" Stude OPENED the canopy rather than JETTISON it as he should have (so it slid back) and he went out. As soon as he departed the aircraft recovered. QFI watched the student's chute open and went home without him.
Second incident: QFI plus student. Aircraft not recoverable from spin. Both jumped. QFI fell out of harness as his chute opened, presumed to have inadvertantly rotated QRF box to "unlock" as he climbed out (possibly due to a mind-set about the normal a/c egress after landing which involved leaving the 'chute in the seat) and then it probably got knocked to release during the chute opening.
After that I always used to leave the aircraft with my parachute on so that I NEVER unlocked the QRF box whilst sitting in the aircraft. (Effectively every egress was an emergency one as far as parachute wearing was concerned; less chance of me incorrectly repeating history!)