A FORMER police constable has told a jury he punched an inspector in self-defence after he caught him having sex with his policewoman wife on the back seat of a car.

Gavin Harper, 45, discovered the couple in a Screwfix car park in Birkenhead, late in the evening of February 16 2021 after he placed a tracker device on his wife’s vehicle.

The security officer said he had suspected for months that Merseyside Police colleagues Stephanie Glynn, 40, and Andrew McLullich, 42, were having an affair.

Harper is on trial at Liverpool Crown Court accused of unlawfully wounding Mr McLullich and stalking Ms Glynn between December 2020 and February 2021.

Giving evidence on Tuesday, he told his barrister, Suzanne Payne, that he did not drive to the car park with the intention of fighting the inspector.

He said: “I was not going there for violence.”

Miss Payne asked: “What did you think you needed to do?”

Harper replied: “Get undeniable proof they were having an affair, a sexual affair, by videoing it and then giving it to the police.”

Miss Payne said: “For what purpose?”

Harper said: “That two serving officers were having an affair during Covid.”

He said that as he approached Mr McLullich’s car he could see he was “clearly having sex with someone”.

He went on: “I looked through the window and I could see he was in fact having sex with Steph.”

Asked why he then opened the rear passenger door as he filmed on his mobile phone, he told the court: “To get better footage I suppose. So that they knew I had the undeniable proof of what they were doing.”

Miss Payne asked: “Was anything said?”

The defendant said: “I can’t remember what exactly I said. It was something along the lines of ‘I’ve got you now, I’ve caught you now’.

“Steph screamed and said ‘it’s Gav’.

“I was upset but weirdly relieved.”

Miss Payne said: “Were you angry?”

Harper, of Ailsa Road, Liscard, Wirral, said: “No, far from it.”

He said Mr McLullich started punching him “repeatedly”.

Miss Payne asked: “You tried to defend yourself?”

Harper said: “I did punch him – three, four times.

Miss Payne said: “Did you carry on defending yourself?”

The defendant replied: “No. I didn’t have the energy for one thing. I was not there for that.”

He said he was then “leg-sweeped” by the inspector and was punched again as he lay on the floor.

Harper said his wife, who he said was naked from the waist down apart from her socks, told Mr McLullich to “get his phone, get his phone”.

He said in the struggle that followed Ms Glynn then “started kicking him”.

He told the jury: “That’s probably the worse thing about it.”

Harper said he later took his phone out of his pocket and started taking “loads of still pictures”.

The defendant said: “I said something derogatory about his (Mr McLullich’s) penis. He didn’t like that. He flew into a rage and he punched me a couple more times to the face.

“Steph got between us and he stopped it.”

The Crown say Ms Glynn started a sexual relationship with Mr McLullich after she left Harper and he could not accept the breakdown of their marriage.

He became obsessed over it, say the prosecution, and it was he who attacked Mr McLullich in the Screwfix car park.

Harper said he initially became suspicious about the pair when he noticed his wife’s car phone call history had “lots of calls” from Mr McLullich.

He said Ms Glynn told him she was his mentor at work and he was helping her through her police sergeant’s exam.

He told the court: “I knew something was going on but I couldn’t prove it. I would repeatedly ask her and she said ‘it’s in your head, it’s in your head’.

Harper said he decided to activate the microphone on the vehicle tracker and move it from the boot to underneath the driver’s seat which enabled him to listen in real-time from an app on his phone.

He said one conversation between the pair confirmed his suspicions.

Harper said: “They were talking about a previous night shift when they had met up and they had some sort of sexual activity, and they were laughing about who was going to sit in the wet patch of the police car.

“I was upset. I now knew something was going on but I didn’t have anything concrete to say anything to her because she would just deny it.”

He went on to download her Snapchat phone history on to his device and discovered an “absolutely massive amount” of messaging between the pair, he said.

Harper said he used his ex-wife’s phone to call Mr McLullich.

The defendant said: “He said ‘hi gorgeous’ and I said ‘it’s Gav, Steph’s husband’. There was then a pause and then ‘oh shit’.

“He begged me not to tell the police and not to inform them what had been going on. He implied he and Steph would lose their jobs.

“He begged me not to tell his wife and not to spoil his children’s Christmas.”

Harper said Mr McLullich denied he had slept with Ms Glynn but admitted there were “inappropriate messages and videos and he agreed they were disgusting”.

The trial continues.