Complex sentence: It finally closed on 23 December 1982, by which time 1,286 people were working there after being in operation for 125 years and pushed Brierley Hill's already high unemployment levels even higher.
Split into simpler sentences: It finally closed on 23 December 1982, by which time 1,286 people were working there. After being in operation for 125 years its closure pushed Brierley Hill's already high unemployment levels even higher.