56062 was working the empty stone train from Ardingly to Westbury when it passed the signal protecting the Brighton mainline at Copyhold Junction and was derailed on the trap points. The loco ended up at the foot of the embankment.
I was working as Chief Clerk Haywards Heath travel centre at the time so a short walk from work got me to the site of the derailment.
This slide is dated 14/6/88 which I think is the day after the event.