History will be made in Calcutta on Wednesday when Indian off-spinner Harbhajan Singh bowls his first ball in the second Test match against Pakistan.

He will be the first alleged thrower to benefit from a new regulation which came into force on March 1 and legalises a previously suspect action.

Nearly 50 years ago the late Sir Don Bradman led a crusade against chuckers who, then, were mostly fast bowlers such as Australians Gordon Rorke, Ian Meckiff, West Indian Charlie Griffith and Surrey's Peter Loader.

Now, spinners such as Singh and Muttiah Muralitharan have crept into the murky world of bent elbows, with the fast brigade still represented by Shoaib Akhtar and Brett Lee.

The key phrase in the new law is "15 per cent tolerance" and that means anything under that level is unable to be picked up the human eye and is therefore allowable.

At the centre of the row surrounding the new law is Chris Broad, the former England opener, who has recently been appointed to the International Cricket Council's elite panel of match referees.

The same Broad was fined in the 1988 for knocking his stumps over in the Bicentenary Test in Australia after being bowled for 139. His inability to accept a decision with which he disagreed was taken to the ultimate at Lahore in 1987 when, given out caught behind when he was a foot away from the ball, he crossed his legs and refused to walk.

Partner Graham Gooch walked down the pitch and told him he had to go, thus saving a major incident turning into something which was a career-threatening incident of terminal proportions.

A fat lot of good that did the peacemaker Gooch when, first over after tea, he also fell foul of the same trio, bowler Iqbal Qasim, wicketkeeper Ashraf Ali and umpire Shakil Khan.

Broad could thus be described as poacher turned gamekeeper but, to his credit, he has refused to back off when he thinks the best interests of cricket would be served by calling it as he sees it.

He has had the guts to report the actions of Muralitharan and Harbhajan as unsatisfactory, particularly when they bowl the "doosra" - the new delivery for an offspinner which spins from leg to off with no apparent change of action.

The previous law on throwing was never drawn tightly enough to withstand a legal challenge, hence the appointment of a distinguished panel to change the law.

A six-man committee was formed, comprising Aravinda de Silva, Angus Fraser, Michael Holding, Tony Lewis, Tim May and David Richardson - a shrewd mix from five countries with a combined total of 294 Test caps so their acceptance of new biomechanical evidence is not to be condemned out of hand by the purists.

This carefully-researched evidence appears to prove that the purest of actions to the human eye, such as those of Allan Donald, Glenn McGrath, Shaun Pollock and Darren Gough all involve a degree of straightening. Hence the ICC explanation that the new law "seeks to deal with the extension of the arm that is visible to the naked eye."

It goes on: "All bowlers will be permitted to straighten their bowling arm up to 15 degrees which has been established as the point at which any straightening is visible to the naked eye."

That is the worrying clause. Broad reported Muralitharan and Harbhajan but both spinners have been cleared after exhaustive tests in Australia in which they bowled barechested with wires connected everywhere to help the 12 bio-mechanic cameras read the legitimacy of the actions.

Their "doosra" was cleared. Namely, whatever aroused Broad's suspicions has been declared as under 15 degrees yet ICC insist that the human eye can only detect an irregularity of over 15 degrees.

Harbhajan and Muralitharan have raised eyebrows all around the world, making the new 15 degree of tolerance appearing to be fixed to accommodate them.

The ICC, not unknown to fudge the odd issue, say: " Referees and umpires still retain the responsibility of reporting doubtful actions which will be determined by scientific laboratory analysis. Any player reported twice and proven illegal within a two-year period will be suspended for 12 months."

The question is still begged about the fixing of 15 degrees as allowable. That means that the suspect doosra will still be permitted. In which case, Murali and Singh are in clover. Except that Broad is match referee in Calcutta in 48 hours' time and will not compromise.

Even if Singh bowls as he did in his Australian Tests, where he was adjudged under the new limit, Broad will report him if he seems the same as before. Human eyesight is a peculiar attribute and Broad might still put the scientists to the test.

The saving grace of the new legislation is that it should keep the lawyers at bay. Even so, that is no justification for bad law. The world awaits Calcutta and Broad.