Soho- A uniformed cop twiddles with a knob on his radio-as a porn star performs a sex act on him in a shameful clip from a secret video.

Minutes earlier the officer and a colleague had been called to calm down a crowd who spotted a blue movie being shot in a Soho street.

But instead of sorting out the dispute then leaving, they decided to meet the stunning twins starring in the film.

The PCs-aged 30 and 34-talked their way into the crew’s parked van and suddenly dropped their trousers.

And the two blondes, who had caused a stir by walking around the streets in micro-skirts, immediately accepted the invitation. As they performed a sex act on the coppers, stunned crew secretly started the cameras rolling.

The men grinned at each other as one exclaimed: “This is perks of the job.”

But amid the moans of ecstasy, another sound could be heard-a crackling radio with a suspicious colleague demanding to know what the cops were up to.

A team of six from the Central London Territorial Support Group had been sent to sort out the trouble. One could be heard asking over the radio: “Zero Three, Four Four. Where are you?”

Even that did not trouble the PCs. As one of the blondes kept up her performance, he casually radioed back: “Yeah, all right, we’ll be there in a few minutes.”

Later the radio went again demanding their whereabouts. A cop-STILL receiving attention-replied: “We’re just going to sort something out. We’ll get back to you in a few minutes.”

The pair let the girls play with their handcuffs-and one even wore an officer’s police cap as she set to work in the van, which had deep-tinted windows and an electric king-sized bed.

Shocked Marino Franchi, directing the movie Twin Cheeks II, said last night: “I have never seen anything like it.

“I never thought serving officers could act like that. And in front of all of us as well.”

Pony-tailed Franchi, who has starred in a string of porn movies himself, added: “I was just expecting them to want their photo taken with the girls or get an autograph.

“It was unbelievable. They just decided to have their very own private porn movie while on the job.

“What they did was disgusting. We filmed it secretly and will put it on the website www.hornypoliceman.net.”

Both men, who deserted their posts while London is on terror alert, eventually felt the call of duty and left the van.

But last night they were suspended and facing a probe. Scotland Yard said: “We can confirm a disciplinary investigation has been launched.

“Allegations concern the conduct of the officers on duty in Soho during the evening of July 26.

“The Metropolitan Police Service demands the highest standards.

“We are disappointed by the conduct which, if substantiated, brings the service into disrepute.”