Complex sentence: Earliest records indicate a regatta took place annually on the River Thames in Marlow from 1855 the latter transferred to the purpose built Dorney Lake, owned by Eton College, in 2003.
Split into simpler sentences: Earliest records indicate a regatta took place annually on the River Thames in Marlow from 1855. The latter transferred to the purpose built Dorney Lake, owned by Eton College, in 2003.