When 1,000 of them march across London on Saturday, led by women sitting in carts, whipping "human ponies" through the streets as part of a weekend of "pervery", they may well look a mite strange to passers-by.
But behind the annual S&M Pride march and the workshops on how to enjoy S&M with standard office equipment (mainly paper clips and rubber bands) lie the eminently serious purposes of safe sex, legal reform and the intellectual justification of pain.
At workshops S&M technocrats will outline in great detail how to be a safe sadist.
"We're very responsible," said Spencer Woodcock, a spokesman for the march organisers. "Education is very important. Tying people up is complicated. We go down to the smallest detail, like explaining how nerves in the thumb can be cut if you make a mistake with the knots."
A fellow organiser agreed. "Safe S&M is like driving a car," he said. "If you don't learn how to do it properly, you can go out there and hurt someone."
Sadism and masochism, despite their influence on fashion, still remain beyond the confines of conventional society, as their advocates realise despite their protestations of respectability. Many of them will be wearing masks on the march. "Wearing a mask," say the organisers, "ensures anonymity and also looks very pervy."
There are bridges being built, however, with the rest of society. Last year Scotland Yard officers came to workshops to assure the demonstrators that Sir Paul Condon, Commissioner of the Metropolitan Police, had no interest in prosecuting consenting adults. This year the emphasis will be on understanding the law.
Members of a libertarian strand of the feminist movement, Feminists Against Censorship, will be on hand to counter arguments from more conventional women's groups and maintain that sado-masochistic pornography does not degrade women but often makes them seem powerful and in control.
The image of responsible sado-masochists will be reinforced later this year when some of the best legal minds in Britain and Europe pronounce on what was the defining moment for the S&M movement, the Operation Spanner case.
The bizarre trial was in 1990. Fifteen homosexuals were convicted and in many cases jailed for practising acts of "genital torture" on each other with nails, canes, scalpels, sandpaper and nettles. Their sexual practices sounded dangerous to most observers, particularly the trial judge, James Rant, who made no attempt to disguise his disgust.
But in 26 years of assaulting each other, not one of the homosexuals had been hurt badly enough to be taken to hospital, and no one had complained to the police. All had consented. In three months, the Law Commission, which advises the Government on law reform, will pronounce on the case. It has been having difficulties inframing a law so that boxing, for example, would not be made illegal but excessive sado-masochistic violence would.
The Spanner trial manoeuvred around the difficulty that all the adults had consented by charging them with "aiding and abetting assaults on themselves".
After months of consultations, the commission seems likely to recommend some changes. Consent will be a defence for both a sadist and his or her masochist partner, as long as the injuries are "not serious".
Supporters of S&M rights believe this does not go far enough. There could be endless disputes in court about what is and what is not a "serious injury", they say, unless a specific definition is given.
John Wadham, legal officer of Liberty, said that what was needed was a "clear statement that the state had no right to interfere with the private lives of consenting adults". The civil liberties group is pinning its hopes on the European Commission of Human Rights in Strasbourg, which is expected to rule on the case early next year.
For the marchers on Saturday, the Spanner defendants are heroes and martyrs, men whose treatment by the courts brought them out of the shadows and onto the streets. The march is dedicated to Colin Laskey, a Welsh rugby referee, from the Rhondda, who died after a heart attack earlier this year.
Instead of hanging his head in shame after he was jailed for four months, he went back to Pontypridd, faced his former rugby club friends and campaigned energetically and angrily to have his name cleared.
"We were all law-abiding citizens in bloody good jobs, who simply never thought that we were breaking the law," he said before he died. "We would go and stay with each other for the weekend. And then after the activity have a cup of tea or coffee together. Where was the hostility in that?"Reuse content