Rubin, though, stuck boldly to her task and dragged it back to 4-4 - only for her 30-year-old rival to break her again in by far the longest game of the match and then comfortably hold serve to clinch victory.
Mr Cameron told BBC Radio 4's Today programme his task now was to deliver a "sense of mission" that the government was focused on issues "squarely in the national interest".
Top seed Federer was taken all the way by Latvian Ernests Gulbis before going through 6-2 4-6 6-4, while Nadal had a simpler task to overcome Belgian Steve Darcis -- who retired while trailing 6-1 2-0.