Quite what the listeners made of this remark is not clear. But all over Whitehall - at the Home Office, the Department of Health and the Cabinet Office, where Mr Hellawell is based - civil servants cringed with embarrassment. The gaffe - doctors can indeed prescribe diamorphine, provided they have a special licence - illustrates a recurring criticism of the UK anti-drugs co-ordinator, to give him his proper title: that he has failed to grasp the detail of his job.
"He is aloof, uninspiring and out of touch," said a senior academic in the drugs field yesterday. "Worst of all, he is out of his depth. He is simply not bright enough. He can't hold all the balls up in the air."
Harsh words, but they were not untypical of the views expressed by drugs experts and voluntary workers yesterday, 16 months after Mr Hellawell was appointed by the Government to spearhead a new anti-drugs crusade.
Mr Hellawell, a former chief constable of West Yorkshire, was selected for the pounds 106,000-a-year post because of his long-standing interest in drugs issues and his reputation for being prepared to "think the unthinkable".
Ironically, the initial concerns expressed about him - that, because of his background, he would concentrate exclusively on law enforcement aspects of the job - have proved unfounded. In fact, he has shifted the emphasis to education and rehabilitation, making clear that he believes the problem cannot be solved by simply arresting and locking up addicts.
His 10-year strategy, unveiled in April last year, included a new penalty obliging criminals to undergo treatment for drug addiction. It also promised improved drugs education in schools and the establishment of a national Drugs Prevention Advisory Service to support local drug action teams in the community.
Even Mr Hellawell's detractors say the strategy looks good on paper, encompassing every conceivable angle. There is also grudging admiration for his success in squeezing pounds 217m out of the Treasury to implement it.
But there remains widespread scepticism about whether Mr Hellawell, a former miner who now drives a Porsche, has the authority, courage and vision to pick his way through the political minefield and make real progress in the fight against drugs.
Many observers draw a contrast with his deputy, Mike Trace, who is seen as brighter, more accessible and more in touch with youth issues. Mr Trace, who rides a motorbike, is a former social worker who worked in the voluntary drugs field.
"Mike Trace holds the whole thing together. He has a far better grasp of the detail and he works his socks off," said one Hellawell critic. "He is immensely relaxed and well- respected."
Out in the field, experts picked their words more carefully. Mr Hellawell, after all, is the public face of government drugs policy and voluntary agencies are largely dependent on government funding. "It would be suicide to criticise him," said one.
Roger Howard, chief executive of the Standing Conference on Drug Abuse, was among the few prepared to speak on the record yesterday. He praised Mr Hellawell for his willingness to heed the views of people working at the sharp end.
Mike Goodman, director of Release, the drugs charity, described Mr Hellawell, diplomatically, as a safe pair of hands. "Certainly we could have done worse," he said.
"He's not a great communicator, but he is amiable, and parts of his strategy are very good. I wish that he would be more outspoken sometimes, that he would tackle the difficult issues such as decriminalisation, which I believe that he supports."
This is a persistent criticism made of Mr Hellawell: that he has abandoned his liberal, occasionally maverick, views and is toeing the Government's hard line on drugs.
As a police officer, he was prepared to advocate reform of the "absurd" laws on prostitution and the legalisation of brothels. He also said, in an interview on the BBC's Panorama programme, that he foresaw the day when cannabis would be legal. After being appointed to his post, he disowned that comment.
There is no doubt that Mr Hellawell is in a difficult position. He is "drugs tsar", modelled on an American concept, but unlike his American counterparts he has no budget, no independence and no real power. He is, in reality, just a special adviser, yet, unlike other government special advisers, he has a high profile.
There is no doubt, too, that he has suffered from snobbishness and elitism at the hands of some senior civil servants, who resented an outsider - and, worst of all, a police officer - being parachuted in above their heads. "What's a copper doing in Whitehall?" people would whisper after he arrived.
One government adviser on drugs, who knows him well, said yesterday: "There were people who fell over backwards at drinks parties when he was appointed. In reality, he has not done badly. But he does not have the sagacity to understand the larger issues. I doubt that the benefits of his job are worth the cost."
Another observer described his appointment as a poisoned chalice.
"New Labour has unloaded the political embarrassment of its failing drugs policy on to the drugs tsar," he said. "As a figurehead, Keith Hellawell serves that purpose."Reuse content