Complex sentence: Rædwald and his son Eorpwald both ruled as pagans before being converted to Christianity, but after Eorpwald's murder in around 627, the East Angles reverted to heathenism, before Christianity was re-established by Sigeberht.
Split into simpler sentences: Rædwald and his son Eorpwald both ruled as pagans before being converted to Christianity. After Eorpwald's murder in around 627, the East Angles briefly reverted to heathenism, before Christianity was re-established by Sigeberht.