This last July, on a searingly hot day, as the tennis player Andy Murray closed in on a historic sporting achievement — to be the first British man to win a Wimbledon singles title since Fred Perry in 1936 — the BBC cameras kept shifting their gaze from one key character to another as the match entered what would be its final game.

The first was, of course, Mr. Murray, a tortured expression on his face as one match point after another eluded him. The other was Novak Djokovic, grimly digging in as he tried to reclaim the title he had won two years earlier.

The third, however, was not on the court at all but in the stands: a striking young woman in a green lace dress captured by the cameras alternately cheering, grimacing and then covering her eyes when the spectacle on Center Court became too nerve-racking to watch.

That woman was Kim Sears, the longtime girlfriend of Mr. Murray. Her much-chronicled romance with the Scot has made Ms. Sears, an artist whose specialty is animal portraiture, as famous in Britain as any actress, model or member of the royal family.