A married police officer has been jailed for three years this afternoon after breaking the law to please his mistress.

Love cheat Alan King – who was in line for a bravery award – had sex on duty with a secret lover.

Then the 48-year-old took cannabis, which he came across in a stabbing investigation, and gave it to Gravesend betting shop worker Zoe Barham.

But now – after a jury at Canterbury Crown Court convicted him of three serious charges – his 25-year career is in ruins.

His wife and family wept as Judge Adele Williams told him he had been obsessed with his girlfriend and wanted to impress her.

"Police officers should be beyond reproach," she said. "They should be people that the public can look up to and have confidence in that they will uphold the law.

"But you broke the law and perverted the course of justice."

As he was being led away, King blew a kiss to his wife in the public gallery and his son shouted: "Love you dad!"

King, of Pankhurst Road, Hoo, had denied three charges of misconduct in office, perverting the course of justice and supplying drugs.

Ms Barham – who said she did not know the amorous PC was married when they

began their affair – had old a jury: "He promised me everything. He promised me a lot. He told me he loved me and I believed him at the time."

Prosecutor Rebecca Fairbairn had said: "In June 2011, King was a serving police constable with Kent Police.

"At the same time Zoe Barham was employed at Betfred betting shop in Gravesend."

She said Ms Barham was witness to an incident when the police were called and PC King investigated.

After giving her statement – which also included her telephone number – she was asked by King if she was working the following Saturday.

She told the officer she was off duty because it was her birthday – only to receive an unsolicited text message wishing her happy birthday sent from the officer's police mobile phone.

Ms Barham said the two then began a relationship in which the uniformed officer would frequent the betting shop – until he was given a warning by a superior officer.

"He later gave me his personal number because he wanted to start a relationship. We met in Forge Lane in Gravesend and he took me back to his home.

"I wasn't aware about his relationship at first but I did suspect after a little while (he was married)."

She said they regularly met either in Forge Lane or at the Gala Bingo car park in Dartford.

"He would turn up in his marked police car and if I was at work we would just talk and have a fag. He would sometimes take me to my home which was in Old Road West in Gravesend in his police car.

"On one occasion he took me up an alley in Barr Road where we had sexual intercourse in his police car. That happened on several occasions.

"Mr King picked me up in his police car and took me there and he was in uniform. I went there because I was in a relationship with him."

She also claimed King - who was based at North Kent police station in Northfleet - took her with him on three occasions while he was investigating incidents and was allowed to input information into the vehicle's police computer.

Ms Barham told the jury she had used cannabis. She said in 2012 King rang her up to ask if she needed "cannabis, weed or green" and she agreed.

The prosecution revealed the police officer had seized the drugs during an investigation into a man who had been stabbed in the neck in the town.

She also told how that the officer had accessed a Kent Police crime database used to store highly sensitive information on victims – to find out details about his lover.

She said the affair ended when the two were arrested in relation to an alleged fraud, although no charges were brought against either of them.

Ms Fairbairn said Ms Barham then told police about what had been going on, adding: "She old them about the drugs."

King has been suspended since the investigation and will now be sacked.