Of course it is not a grand slam; nor can it be, by definition. If Tiger Woods wins the US Masters on Sunday, for his fourth consecutive major championship triumph, that is exactly what it would be: four-in-a-row.

It would be, by some distance, the greatest accomplishment in golf so far. There is no denying that and no wish to deny it. But the golfers of the recent past, though paying tribute to Woods, maintain that four-in-a-row is not a grand slam unless completed in a calendar year. That is how it started, that is the concept and no other will do.

No one has ever completed the modern grand slam. To do so the player has to win, in the same season, the US Masters, the US Open, the Open Championship and the US PGA. In terms of winning championships Jack Nicklaus, Arnold Palmer, Gary Player, Ben Hogan, Sam Snead, Gene Sarazen, Tom Watson and Lee Trevino have all come and gone. Some got close to the slam but it remains what the old-time golf writers called it, the Impregnable Quadrilateral.

Most modern golf writers, including this one, have routinely dismissed the chances of it ever being done. To win a single major requires such a confluence of factors - peak form, complete fitness, great good fortune - that many of the best players either win only one or two in a career or even none at all.

For those factors to recur precisely in the four weeks of the year that host major championships seems so unlikely that the possibility has never seriously been entertained. Nicklaus always said that a grand slam was possible but not probable but there was always a sense that this man, who won 18 professional majors, and five times won two in a season, was keeping the door open simply because he could not bear the thought of it being shut.

But now there is Woods, the 25-year-old who is rewriting the record books. No fewer than 27 went, or were equalled, last year, and of those the most significant was that he became the first man since Hogan to win three consecutive majors. In 1953 Hogan won the Masters, the US Open and the Open Championship but could not get back to the States in time to play in the US PGA.

Some 47 years later Woods won the 2000 US Open; the Open Championship (completing a career grand slam) and the US PGA in a play-off with Bob May. Now the 2001 Masters looms, the first major since he won the US PGA, and Woods wants us to believe that, if he wins, it will mean he has completed a grand slam. At Bay Hill two weeks ago he was asked: "If you won the Masters this year, would you consider that a grand slam?" His reply? "You know, hopefully, if I win the Masters, it will be considered the slam. And in my estimation it would be, because I would hold all four at the same time."

To which Player and Nicklaus, the only living golfers other than Woods to have completed a career grand slam, reply, in effect: "Balderdash".

Player, nine times a major champion, was almost incandescent at the suggestion. Before the question was completed he jumped in. "Ab-sol-utely not," he said. "No. It's a yearly thing. Who won the Masters last year? Vijay? Well then, he had the chance last year. A grand slam is one thing, a career grand slam is quite another."

The suggestion that perhaps four-in-a-row could be considered a grand slam because the competition was harder these days than it was when Player was playing brought him near to critical mass.

"Harder?" he echoed. "It's easier, much easier for Tiger to win majors these days. Look at what Jack [Nicklaus] had to beat when he was winning 18 majors. There was Arnold Palmer, Lee Trevino, Tom Watson, Raymond Floyd, Billy Casper - even myself. We all had multiple majors.

"I don't see many multiple major winners competing against Tiger. Ernie [Els] has got two, Phil Mickelson none, Davis Love III has got one. I don't see these as superstars yet. They've got to prove themselves. Jack's opponents had all proved themselves."

Not that Player has any doubts about Woods's talent. "Go back 60 years," he said "to Hogan and Snead and Byron Nelson for a team of three. I'd put Tiger in against those, but who would be the other two? I don't see anyone else to join him."

Nicklaus, typically, is more succinct. He never really got close to a calendar slam, his best effort being in 1972, when he won the Masters and the US Open and then finished second in the Open Championship at Muirfield, to Trevino.

Despite the fact that he is obviously the oracle on the subject, he said: "I really don't think I'm the person to determine that. A grand slam is winning all four of them in one year. But what is your year? Calendar or fiscal, so to speak. I don't know but it would be pretty special whatever it is."

Palmer not only missed out on a calendar slam; he failed to win a career slam as well, never triumphing in the US PGA. But that did not stop him from being vehement about a genuine slam needing to be competed in one season.

To the suggestion that Woods could win a grand slam at Augusta he said: "That is ridiculous. If he wins there he is starting a new cycle; it's not a continuation of last year. You know, to think he wins the slam this year at Augusta takes the fun out of it, the kick out of it. It's like saying that, if Bobby Jones won the British Open and the British Amateur and the US Open in one year, and then the US Amateur the next year, then he won the grand slam.

"That," said Palmer emphatically, "is not the case." And then, for the removal of doubt as the lawyers say, he said slowly: "It-is-in-one-year."

And Palmer is now, as Jones once was, the authority, the arbiter. It was Jones who began the whole slam thing when he won the four championships mentioned above in one year, 1930. It was the finale of an eight-year period during which he won the US Open four times, the Open Championship three times, the US Amateur five times and the Amateur Championship once.

He then retired and with him went the concept, until it was revitalised, in different form, by Palmer 30 years later. Palmer has written about how the grand slam re-entered golf. After winning the Masters and US Open in 1960, he decided to enter the Open at St Andrews. On the flight to the United Kingdom he had a conversation with a colourful character called Bob Drum, a hard-drinking sportswriter of the old school.

Palmer says: "Somewhere, in an extended cocktail hour, we got talking about Jones's great grand slam. Drum remarked to me that it was a shame that the growth of the professional game effectively ended the grand slam concept and I said, casually over my drink, `Well, why don't we create a new one? What would be wrong with a professional grand slam involving the Masters, both Open Championships and the PGA?"'

Drum, much taken with the idea, shared it with the Guardian's golf writer Pat Ward Thomas among others. His writing helped create it but the seed came from Palmer, who has the right to be as acerbic as he likes on the subject.

And so it is - tough. But that is the way it was meant to be, golf's loftiest goal. And here is a thought for Woods. Should he win at Augusta and call his achievement a grand slam, what does he call it when, if ever he does, he wins all four in a calendar year?