Complex sentence: After leaving the RAF he returned to work at Gedling Colliery, here he was involved in an accident whereby a roof collapsed on him injuring his back and leaving him hospitalised for several months.
Split into simpler sentences: After leaving the RAF he returned to work at Gedling Colliery. During this time, he was involved in an accident whereby a roof collapsed on him, injuring his back and leaving him hospitalised for several months.