Padraig Harrington signed a deal with his equipment supplier yesterday that is estimated to be worth at least $10million (about £6.1 million) over three years and hinted that he had turned down several millions more by rejecting the advances of some of the sport's largest manufacturers.

The winner of three of the past six major championships, Harrington - dressed in a pinstripe suit like the accountant he trained to be - was all smiles as the deal with Wilson was announced in Dublin. And no wonder. “There was competition and the figures were large,” the Irishman said. “But there were other things to take into consideration.”

He has been with Wilson for ten years and, as its marquee player, is guaranteed to be given its full attention. That, as any player will tell you, is worth plenty. “I'm definitely signing the best deal,” he added. “The best policy is to change as little as possible. If I had changed manufacturer and my form dipped, I wouldn't know for sure why. You've got to believe in the product and this takes away the doubt.”

From the moment that Harrington added a second Open Championship at Royal Birkdale to the one he collected at Carnoustie in 2007 and went on to win the USPGA Championship at Oakland Hills, in Detroit, Michigan, in August, his value has rocketed. For a player whose main contract was drawing to a close, the timing could not have been better.

For Wilson, however, it also provided a bit of a headache. Not only did the company have to fork out two large bonuses - undisclosed, but anything up to $1million for each of his major championship wins in 2008 - but it also had to renegotiate Harrington's contract while being made only too aware that the opposition were snapping at its heels.

“This deal will put Padraig in the top four of five [best-paid] players in the world,” Tim Clarke, general manager of Wilson's golf division, said. “He was in a very strong negotiating position because others offered much more money than we could afford. I was aware of the companies [reportedly Callaway and Bridgestone] that were going after him. But we were about the whole package. For many, it is all about the dollar. But Padraig is all about integrity and faith. We feel we both have a fair deal.”

According to Clarke, if Tiger Woods is taken out of the equation, the leading eight players - among them Phil Mickelson, Vijay Singh and Ernie Els - can command anywhere between $2.5million and $6million annually from their equipment suppliers. On top of this figure can be added considerable performance-related bonuses. In every sense, Harrington is now one of the big boys.

Clarke said that his eyes had watered with some of the figures being thrown around in the negotiations. “Adrian [Mitchell, Harrington's manager at IMG, the management company that also represents Woods] didn't go easy on Wilson, that's for sure,” he said, adding with a touch of understatement: “When Padraig won two majors it changed things. I had many sleepless nights while we were putting this deal together.”

The suggestion that a private jet may be thrown in for good measure, however, was treated more in jest than anything else. “This is not the best time to buy a depreciating asset,” Harrington said, betraying the accountant in him.

Wilson was so determined to hold on to its man that deals with other players were put on hold until Harrington signed on the dotted line. It has lost the company at least one young player in the United States, but Clarke said that he would like a lifetime tie-up with the Irishman.

“He's going to be a Ryder Cup captain one day, a legend in golf,” he said. “We've had only three other players - Gene Sarazen, Sam Snead and Patty Berg - tied in with us for life and we would love to have Padraig finish his playing days with us.”

Roger Federer has a similar lifetime commitment with Wilson. Asked who would be paid more, the tennis player or the golfer, Clarke played coy.

“Padraig is in rarefied air,” he said.

Among the rules of thumb for major championship winners, agents would generally expect their clients initially to double their off-course earnings, with a tenfold increase not uncommon for serial winners. Bonuses can range from $100,000 to $1million and appearance fees will jump substantially, up to $500,000 and beyond.

In his 11 years as a professional, Harrington has won about £14million. By the time his playing days are over, his endorsements are likely to have swamped that figure. That's a pretty good return for a good deal of talent.