Complex sentence: Stukeley conjectured that it belonged to Exuperius, the Bishop of Tholouse in 405 AD, who gave it to the Bouge church in Touraine, and that it only ended up in England after it was plundered as spoils of the Battle of Bouge in 1421.
Split into simpler sentences: Stukeley conjectured that it belonged to Exuperius, the Bishop of Tholouse 405 AD, who gave it to the Bouge church in Touraine. And that it only ended up in England after it was plundered as spoils of the Battle of Bouge in 1421.