Mandatory Credit: Photo by Amer Ghazzal/Shutterstock (12143617m) ROGER FEDERER'S CHAMPION TENNIS BALLS MADRID, 2012 Each signed 'Roger Federer' and printed with 'MUTUA MADRID MASTERS' by Dunlop. Estimate: L500-800. Christies's preview of the Roger Federer collection to benefit the Roger Federer Foundation includes sporting memorabilia and 20 lots from his Grand Slam victories which will be offered for auction in London on 23 June Christie's Roger Federer Collection Preview, London, UK - 21 Jun 2021