I arrived at the Belfry yesterday to watch Padraig Harrington complete his victory round in the Benson and Hedges; it seemed a matter of form that he was going to win.

He arrived on the practice ground the customary hour before his tee time. He hit two wedge shots, and was then approached by Andy McFee and David Probyn, two Tour officials.

They had with them Padraig's card from Thursday. Andy asked Padraig if the signature in the "player's" line on the card was his. Padraig answered no. Everyone knows that Harrington shot an excellent 71 in trying conditions last Thursday. But under rule 6.6b the penalty for failing to sign a correct scorecard is disqualification. Galleries and television cameras are not testament enough under the rules of golf.

McFee said that "this basic rule goes to the core of the game, it must be observed".

The initial reaction of Padraig's caddie, Dave McNeilly, was disbelief. A ghostly pallor swept across his customary happy face; 10 minutes after the news broke Dave was still prepared, in denial of the facts, to go out and win the tournament.

Padraig was more realistic about the news. He immediately phoned his family members. His sister-in-law, who is not a golfer, clarified the relative gravity of the situation for him: he was not reporting the death of a family member, everyone is still alive.

Padraig's other family members, he joked, must think he has a sick sense of humour, because their initial response to his news was also, "you're joking". I was hoping to report on focused, clinical and controlled golf from the Dubliner culminating in the biggest winner's cheque of his career. Instead, I got to witness a stoic performance from him in the press room explaining what happened and who was to blame.

There was an icy silence as Harrington explained that it was his responsibility entirely for what happened. The questions were slow to come from the journalists, and Padraig had to break the ice. "It's the first time I have got the press gob-smacked," he said as he cast his eyes over the sea of reporters, and a wry smile cracked briefly on what we all expected to be a doleful face.

The questions were asked as to how an unsigned card from Thursday took so long to materialise. The Belfry hotel had asked the Tour on Sunday morning if they could have the scorecards of the potential winners for the previous three rounds. They probably wanted to frame them and exhibit them in the clubhouse. Who knows what would have happened if the Belfry were not so keen on golf exhibits?

Although it took a strong personality to say that it was probably for the best that this mistake was spotted now and not at some future date after (assumedly) he had gone on to win the title, Padraig, through teasing questions from the floor, admitted that it was for the best. If he wins, he wants to win "fair and square", with no ambiguities.

Padraig admitted that he scrutinises his card longer than most players; as a qualified accountant it's probably a hazard of the trade, he was always last to leave the scorer's hut. In 16 years of competition he cannot remember making a mistake with his card.

Reflecting on this blunder, he said that the signature of his marker, Jamie Spence, is similar in size and shape to his own. So after seeing two signatures on the card, including one that resembled his own, he was satisfied that everything was in order. Little did he realise that it was Michael Campbell's signature that appeared on the player's line.

Harrington has shown true professionalism and strength of character under the most difficult circumstances. He will look upon this incident as a positive thing. I would not be surprised if he is in contention again next week, with his clear signature on the bottom of all four score cards.