Possible Clues:

• 13 across starts in this date to be for witness
• Was a witness at the set-up with Edward
• The way to get the riot into a tin with a prayer
• Witness that one bore and swore
• Witness a teetotaller with his steed
• Sworn to have done this at court
• Bore witness to death, endlessly raving about trial
• Affirmed wrong date given about international match
• Backed up officially
• Swore to be true