PC Ian Smellie, 64, told colleagues “cameras off” as he removed his police vest and ushered Rafik Miah around the corner at the end of a car stop in Stoke Newington, north London.
The experienced officer is accused of saying to Mr Miah “you think you are a big man”, before allegedly raising his arm to give him a “clip round the ear”.
Smellie denies assault and says he acted in self-defence during the incident on November 10 last year, City of London magistrates court heard.
Prosecutor Emily Baxter said Mr Miah’s car was stopped at around 12.45am after coming under suspicion, and the driver was “rude to officers” while he was handcuffed at the side of the road.
“Once the search of Mr Miah was complete, PC Smellie removed his Met vest and said to other officers present ‘cameras off’”, she said.
“He then guided Mr Miah around the corner by the arm, and officers say he appeared to want to speak with him around the corner.
“Officers describe him then essentially squaring up to Mr Miah and using his hand to hit Mr Miah around the head.
“The other officers present describe being shocked by this, it was not something they expected to happen.”
Bodyworn footage captured Smellie’s initial roadside exchange with Mr Miah, as the motorist complained about being stopped and called one of the female officers a “b*tch”.
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The footage ends moments after Smellie is heard telling colleagues: “Hold on, turn your cameras off”.
PC Nicholas Cousins, who was also present during the car stop, said the instruction “gets said quite often” at the end of a search, when officers forget to switch off their cameras.
He told the court he saw Smellie “ushering” Mr Miah around the corner, adding: “There was some form of interaction between them. I don’t know what was being said.
“I heard PC Smellie say in a raised voice ‘you think you are a big man’.
“With his right arm, he raised it up. It wasn’t a punch, it was a clip motion.”
He added: “I was a little bit shocked as to what was happening, and just wanted to process it myself.
“It was just a very strange way for the stop to end. It wasn’t something I was used to seeing or accustomed to.”
PC Bradley Francis said he heard Smellie saying “go on, try it” to Miah, before “clipping him around the ear”.
“They were squaring up to each other, although Mr Miah is quite a lot shorter”, he told the court.
“There was pushing and shoving from both, and PC Smellie raised his right arm and kind of clipped him around the ear.
“Mr Miah stepped back and has thrown a punch at PC Smellie which didn’t connect.”
In a prepared statement, Smellie told police Mr Miah had tried to attack him, and he had raised his arm “in an instinctive movement to protect myself”.
He said he took his police vest off to stretch his back, having suffered persistent pain in the last few years, and believe Mr Miah “saw it as a possible opportunity to confront me”.
“I was interested to know why Mr Miah thought he could speak to us in the way that he had”, he said.
“Instead of saying anything, he swung his left arm at my head. I swung my right arm out at his arm to block the swing, and stop a follow-up blow from him.”
Smellie added: “I may not have been very professional in challenging Mr Miah to say what he wanted to say, but I did not assault him.”
Smellie, from Holloway, north London, denies assault by beating.
The trial in front of District Judge Samuel Goozee continues.
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