He recently stunned himself with a Taser gun to prove the police device was not dangerous. Then he broke into his own headquarters at night to highlight a lack of security.

And last week Brunstrom’s sanity was questioned after he proclaimed that the illegal drug ecstasy was “a remarkably safe substance” – safer than aspirin.

How does it feel, I ask, to be Tasered with 50,000 volts? “Very uncomfortable,” Brunstrom admits.

He did it for “ethical reasons” to demonstrate that the police’s reassurances were true.

So presumably he’s taken ecstasy for the same reason?

“Never. I don’t take illegal substances. I’ve never touched cannabis in my life. I don’t smoke. I drink a little bit of alcohol but not to excess.”

He says that more people die from taking aspirin than ecstasy.

“Why are heroin and cocaine illegal and not lighter fluid? It is demonstrable that tobacco and alcohol are more addictive and more dangerous than cannabis, yet they are not illegal. The question is not whether I am mad, but why these things are illegal.”

Brunstrom refers to 20 substances listed in a “hierarchy of harm” printed in The Lancet last year.

The league table is headed by heroin, closely followed by cocaine, with alcohol in fifth place, tobacco ninth, cannabis 11th and ecstasy 18th.

If ecstasy, as he stated on Radio 4’s Today programme last week, was “far safer than aspirin” how does he respond to the parents whose children have died after taking a pill?

The policeman has a broad answer: “There has not been a single case of someone dying as a result of being poisoned by ecstasy.

“The most famous case is that of Leah Betts, a young girl who actually died of water poisoning in 1995.

Because ecstasy causes you to be thirsty, she drank too much water. Her brain stem was crushed and her heart stopped. My advice to everybody is don’t take ecstasy in the first place. But why should it be a criminal offence? It may be stupid, but why should you be arrested and prosecuted?”

His latest campaign has prompted the tabloids to replay a peal of clangers by the 52-year-old Londoner. Notable was his decision to display photographs of a headless motorcyclist to a public conference without asking the family’s permission.

There have been calls for his resignation, including a petition last year on the Downing Street website that attracted 3,000 signatures. Why has he invited such vilification? “Because it matters. I think I have a public duty to speak out.”

Even if it costs him his job? “I have the backing of my police authority. There are consequences to being notorious and vilified, of course. But I’m far from alone in this.”

He believes it would be ludicrous to ban alcohol and cigarettes and wants them included in a new substance misuse act – but he admits “nobody knows” how they might be regulated. He also advocates the legalisation of class A, B and C drugs, which would be dispensed by the state and thus deprive criminals of a multi-billion-pound market. He doesn’t want drug-takers needlessly criminalised.

Invoking numerous sources, he claims the war on drugs is unwinnable. “It is not possible to run a democratic country and stop drugs getting in,” he insists. “We reckon, on the best evidence we’ve got, that we stop between 10 and 12% at best of the drugs imported into the UK.”

His assertions on heroin would give most antidrugs campaigners cold turkey. Despite heading his “hierarchy of harm”, he says it is “not particularly dangerous”, although highly addictive. “If taken sensibly, heroin has no known adverse medical effects.”

Brunstrom contends that prescribing heroin to addicts has been proved to reduce their criminal activities: “Because most of their criminal behaviour is driven by the need to gain cash and buy more drugs.”

He rates cannabis as “demonstrably less dangerous and addictive than tobacco”, but concedes that crack cocaine makes people “extremely violent”.

Unable to cite any precedents for the legalisation of drugs beyond the recent case of Portugal, he says the experts know what is likely to work. Of course, a similar confidence inspired legislation on 24-hour drinking.

The difficulty is not that Brunstrom doesn’t have a case, but that he undermines it with obtuse reasoning: comparing the relative safety of ecstasy and aspirin has not left people angry at the absurdity of policy, just thoroughly confused.