A senior officer at Scotland Yard made an “extremely stupid” decision to give the News of the World information about a new police inquiry into phone hacking, her lawyer admitted today.

Detective Chief Inspector April Casburn was reacting in an “angry and emotional way” to resources being removed from the fight against terrorism when she contacted Rupert Murdoch’s tabloid in September 2010, Patrick Gibbs, QC, said.

Appealing to a jury not to convict the officer, who ran the Metropolitan Police’s financial investigation unit into terrorism, Mr Gibbs said that she had been acting out in the public interest when she passed information about Operation Varec on 1 September 2010.

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A NOTW journalist’s note of the eight-minute call stated that DCI Casburn had been seeking to “sell” information about the hacking inquiry to the paper, a claim she describes as 'ludicrous'.

The email was later discovered by a Scotland Yard inquiry into police corruption, Operation Elveden, and DCI Casburn was charged with misconduct in public office – which she denies.

At the end of her three-day trial at Southwark Crown Court, Mr Gibbs described the call as “extremely foolish” and “extremely stupid.”

But, making his closing statement, he said that “a misjudgement, even a bad one” was too low to meet the bar of misconduct in public life.

He added: “If a bomb had gone off on a Tube train when a lot of SO15 [Scotland Yard’s Counter-Terrorism Command] people were interviewing Sienna Miller or Hugh Grant she would look a lot less stupid now, I suggest.”

Minimising her involvement, he told the jury: “We know that the News of the World printed no story, they paid her no money and she never rang again.”

For the prosecution, Mark Bryant-Heron, maintained that the note taken by NOTW journalist Tim Wood, and his subsequent testimony to the court, made plain that she had asked for money.

He also noted how DCI Casburn had added changed her defence several times in the run up to the court case.

He disputed her contention that everything she said in the call had been public knowledge as a result of media reports following a report about hacking in the New York Times on 1 September 2010.

He asked: “If it’s all out there, why the call? What’s it all about.”

He went on: “I’m afraid it’s all about money: ‘I’m on the inside track, I know all of these things, I can be really useful to you if you pay me.’ She was setting out her stall for the future.”

The jury will begin considering its verdict tomorrow.