The co-stars played murderous partners-in-crime in West End musical Sweeney Todd: The Demon Barber Of Fleet Street last year (12), and Ball admits working with the Harry Potter star was a career highlight for him.
He tells Britain's Daily Express newspaper, ""Finding myself opposite one of the best actresses in the country every single night - it was a master class. We both went on knowing we had each other's backs. There was never any ego, any kind of gamesmanship. We just loved doing it together. We riffed off each other. I would burst with pride every night.
""I can't imagine it happening again in my career like this. We became great friends, and there's a mutual admiration. We brought different things to the pie. We come from different sensibilities. But it just worked.
""And we made each other laugh! Just genius and then breaks my heart on stage. So much integrity. I'm a big fan.""
The duo went head-to-head at the 2012 Theatre Awards UK, where they were both nominated in the Best Performance in a Musical category, but it was Staunton who walked away with the trophy in October (12).