I think the Monarch 1’11 incident was 1977, I remember seeing it patched up ready to be ferried out. There was also a Uganda 707 that ran off the side of the runway in the snow and sank in the soft ground, apparently one or more of the reverses failed to deploy. The runway was blocked for quite some time. Normally that wouldn’t have caused much chaos, but there were quite a few Gatwick fog diversions there that day, winter 77/78.
I have heard about several other earlier incidents, Lloyd Britannia nose undercarriage collapse, Air Charter York, belly landing, after undercarriage retracted too early during takeoff! There were also a few fatal accidents in the 50’s.