WHEN Thomas Guerriero came knocking, pulses quickened at Oxford City, a club in the sixth tier of English football. The snappily dressed American appeared to be building a thriving conglomerate that included sports teams and private universities. He bought a 50% stake and talked of propelling the club into the big time.

The tie-up appears to have been an own-goal. Mr Guerriero’s stake has been frozen as he awaits trial in America on ten charges, including fraud and witness-tampering. (He denies wrongdoing.) Oxford City has lost face, but little money: its assets are safely parked with the charity that owns the other 50%. Others have fared worse: prosecutors allege that Mr Guerriero ran a “boiler room”—a brokerage that uses high-pressure tactics to sell shares and other investments of little or no value to unwary individuals over the phone—which bilked 150 American investors out of $6.5m.

Boiler rooms trade on coercion and intimidation, and this one was no exception, say prosecutors. Victims were told that their conversations had been recorded and were legally binding agreements to buy, and that if they reneged they would face late fees and property liens. It is alleged that one even liquidated an annuity to hand over $250,000.

The heyday for boiler rooms was the dotcom boom of the 1990s, when Jordan Belfort, the “Wolf of Wall Street”, strutted his stuff. Today, online and e-mail-based fraud is seen as a bigger problem. But the steady stream of convictions suggests that old-style boilers remain common. The Guerriero case is one of dozens of its type brought by the SEC in recent years.

Crime-busters worry that scams are evolving. While stock fraud has waned, says a regulator, there has been a “significant rise” in boiler-room tactics being used to sell things like carbon credits, fine wine, rare earth metals and even bogus Ebola treatments.

America remains the world’s investment-fraud capital, but police in Britain—where investors lost an estimated £1.7 billion ($2.8 billion) to such scams in the 12 months to September 2014—fret that the City of London could become infested with financial cockroaches. They are leading a multi-agency crackdown. Britain’s Financial Conduct Authority runs a website, ScamSmart, that lists more than 1,000 dodgy operators.