Roger Federer is officially in the building. The 20-time Grand Slam champion is practicing inside the O2 Arena in London as he gears up for the Nitto ATP Finals, which starts on Sunday.

There was the odd flight of fantasy, but Roger Federer’s 6-1, 6-4 win over David Ferrer at the ATP World Tour Finals in London on Sunday was more about functionality. The Swiss got the job done ...