Complex sentence: For over 50 years an annual tug of war with neighbouring Tiddington has taken place each summer across the River Thame: it is the duty of the soaked losers to buy the victors beer.
Split into simpler sentences: For over 50 years an annual tug of war with neighbouring Tiddington has taken place each summer across the River Thame. It is the duty of the soaked losing team to buy the victors beer.