Complex sentence: Founded in 1954 and continuing until 1987, it was originally called the St Pancras Festival until 1965, it specialised in the revival of long-forgotten operas, some of which subsequently made their way back into the repertory.
Split into simpler sentences: Founded in 1954 and continuing until 1987, it was originally called the St Pancras Festival until 1965. It specialised in the revival of long-forgotten operas, some of which subsequently made their way back into the repertory.