Complex sentence: Norton eventually recovered from the attack and now openly jokes about it on-air, although during filming of the BBC 2013 Christmas advert he, by coincidence, had to film in the spot of the attack (unbeknownst to the directors).
Split into simpler sentences: Norton eventually recovered from the attack and now openly jokes about it on-air. However, during filming of the BBC 2013 Christmas advert he, by coincidence, had to film in the spot of the attack (unbeknownst to the directors).