"Oh no, I've done a Titus"
LOL ...
I have tried the same with my 1.9i where that rear stabilizing engine mount (1.6 specific, btw) is shifted to the right on the engine, so the arm connecting the chassis/mountpont and the engine is at an angle. The fist arm was too fragile and broke - luckily on my way home, at the top of the road. The gearlever becomes rather vivid in that situation
Anyway, I don't really understand what happened on your car - the force applied to that mount under acceleration should be flat compression, - how that gets transformed to something which can shear the mounting hole is difficult to understand. ?
I'd like to know how to prevent it happening again
Well - the current one lasted 27 years, so just replacing it with an original should be good enough ?
/Lennart