In July 1708, the Duke of Marlborough, with his ally Prince Eugene of Savoy, won a great victory at the Battle of Oudenarde. On the way to the thanksgiving service at St Paul's Cathedral, Sarah engaged in a furious argument with Anne about the jewels Anne wore to the service, and showed her a letter from the Duke of Marlborough which expressed hope that the queen would make good political use of the victory. The implication that she should publicly express her support for the Whigs offended Anne; at the service Sarah told the queen to "be quiet" after Anne continued the argument, thus offending the queen still further.