On the evening of 5 December 1704 [Johann] Mattheson's opera Cleopatra was being given its second performance at the Gänsemarkt. The composer not only figured as conductor, but as one of the stars, in the role of Antony (the libretto follows the well-known historical outline). Having fallen on his sword and had his death scene, he was then at liberty to slip into the pit and take over at the harpsichord. Handel, who had migrated from second fiddle desk to the keyboard, now refused to budge, though Mattheson, as director of his own opera, had an acknowledged right to take over.
Furious with each other, they managed to get to the end of the show, while several of the orchestral players egged them on. There was a challenge at the stage door, a crowd gathered, the two men drew their weapons and set to in the open market place outside the theatre. It was a duel which, as Mattheson tells us, 'might have passed off very unfortunately for both of us, had God's guidance not graciously ordained that my blade, thrusting against my opponent's broad metal coat button, should be shattered.'