text: One letter addressed to this ruler discussed the problem of merchants who mingle among pilgrims, demanding that those false pilgrims pay road tolls, while another letter addressed to him discussed the expulsion of a priest for eating meat during Lent.
full_question: One letter addressed to this ruler discussed the problem of merchants who mingle among pilgrims, demanding that those false pilgrims pay road tolls, while another letter addressed to him discussed the expulsion of a priest for eating meat during Lent. This king expanded his territory by winning the Battle of Bensington, and founded an abbey at Winchcombe, which contains the Monk's Walk. He convinced Pope Adrian I to split the Archdiocese of Canterbury into two halves. His daughter was set to be married to Charles the Younger, until it was called off because this ruler offended Charlemagne. This king introduced the silver penny as currency during his reign, and depicted his allegedly-evil wife Cynethryth on the coin. He took power by defeating Beornred in a civil war after the murder of Aethelbald in 757 CE. This king is also known for marking the boundary between Wales and his territory by digging a 149-mile long series of ditches. For 10 points, name this great king of Mercia who built his namesake Dyke.
first_sentence: One letter addressed to this ruler discussed the problem of merchants who mingle among pilgrims, demanding that those false pilgrims pay road tolls, while another letter addressed to him discussed the expulsion of a priest for eating meat during Lent.
raw_answer: Offa of Mercia