Complex sentence: Einar spent the summer of 1977 in London, where his father worked-through this he was able to make contacts enabling the Reykjavik arts festival to book The Clash in 1980.
Split into simpler sentences: Einar spent the summer of 1977 in London, where his father worked. Through this, he was able to make contacts enabling the Reykjavík arts festival to book The Clash in 1980.