Complex sentence: Tom was a Merchant Marine who had been friends with Mark Fowler, Ian Beale and Sharon Watts when they were children, but left the Marines in 2002 and is first seen at the funeral of Sharon's mother Angie (Anita Dobson).
Split into simpler sentences: Tom was a Merchant Marine who had been friends with Mark Fowler and Sharon Watts when they were children. Tom had left the Marines by 2002 and is first seen at the funeral of Sharon's mother Angie (Anita Dobson).