The 25-year-old German, who exudes much the same calm as Bernhard Langer, had left any nerves behind after he and Watson tied at 11 under. "The pressure," he said, "had kind of gone because the worst you can do is finish second. Of course you want to win but I felt relaxed. I only had to beat one guy and that was it."
Before they set out, Kaymer and Watson had spared more than a thought for Dustin Johnson who would have accompanied them but for a ruling which will presumably be the subject of much official debate. Johnson was three under par and one ahead playing the 72nd when he hit into a patch of sand in the right rough. It never struck him for a second that it counted as one of the 1,000-plus waste bunkers on the course.
It was only after he had missed the six-footer which people thought he had for the championship that he was approached by an official. The latter put a hand on his shoulder and explained that if he had grounded his club in the sand, he was due a two-shot penalty.
Since Johnson could not say for sure that he had not, the penalty was applied and his tournament was over. "The only worse thing which could have happened to me," he suggested, "would have been if I'd holed my six-footer and been told then."
As Kaymer and Watson returned to the course, the sorely dejected Johnson went on his way with a sad, "I gotta deal with it."
The German and the American were level when it came to the 18th, the third and last of the play-off holes and it was Watson who had the first crack at the second shot. He went for the green - a carry of 210 yards over water - but, to his horror, his ball ended up in the hazard.
Kaymer, who already had five European Tour titles to his name, promptly decided to play safe and won the hole with room to spare.
Watson pre-empted the question as to whether his had been a good decision. "Before you ask," he said, "if I had to do it all over again, I would hit that shot every day. I don't play to lay up, hopefully make a putt and tie."
Where Johnson finished in a share of fifth place, Rory McIlroy, another who had come within a whisker of making the play-off, finished in a tie for third with Zach Johson on an afternoon when he was left kicking himself over the shots which had got away down the stretch. Having been tied for the lead with four to play, he had a three-putt green at the 15th and an iron which failed to come round on the wind at the 16th. Yet, with two top three finishes under his belt from this year's majors, the Irishman has to fancy his chances of bagging one of the four in 2011.
Nick Watney went into the final round with a three-shot lead but not enough sleep. He had woken at four and at six and, at eight o'clock, he finally gave up on the idea of getting any more rest. Butch Harmon, his coach, could see that he was rushing things on the range and the same applied on the course as he started with a double-bogey. Kaymer went ahead as early as the fourth where Watney and Johnson both dropped a shot as the wind started to hammer at the course.
Last year, Kaymer broke four bones in his foot in a go-carting accident which left him on the side-lines for two months and limping for rather longer. The injury gave him the space to ponder on his dreams, two of which he has now accomplished - winning a major and securing a place in Europe's Ryder Cup side for Celtic Manor.