Complex sentence: On 1 June 1984, Venom accidentally burned Hammersmith's ceiling during a performance of "Countess Bathory", which event can be clearly seen in the 7 Dates of Hell concert video.
Split into simpler sentences: On 1 June 1984, Venom accidentally burned Hammersmith's ceiling during a performance of "Countess Bathory". This event can be clearly seen in the 7 Dates of Hell concert video.