A trainee driving instructor who shot a man twice through the head in a café was jailed for life yesterday.

Gary Oxley, 48, had gone to the police five weeks before to say he was in fear of his life - but had then taken the law into his own hands.

Mr Oxley, from Mottingham, south London, pleaded guilty to murder and was told he would have to serve a minimum of 21 years.

Old Bailey judge Peter Thornton told him: "You walked calmly and coolly into the café. This was a deliberate, calculated and planned execution. You killed in cold blood."

The court was told that on March 4, Mr Oxley went to the DA Sandwich Café near his home to meet two men. He walked past them as they sat opposite each other drinking coffee.

After pulling a revolver from his waistband, the man facing him ran off, but Joseph Olliffe was shot in the back of the head at point blank range.

Mr Oxley then dialled 999 and told them he had done it because he and his family were being threatened by gangsters over drugs and a £6,000 debt.

The judge said Mr Olliffe and the other man had tried to collect the debt on behalf of a Mr B who was in prison. "They threatened you and, through you, members of your family."

Mr Oxley had gone to the police on January 29 to complain about blackmail but did not say what the debt was for.

The judge added: "The police took the allegation seriously but were not able to prevent further serious threats, particularly since you failed to keep subsequent appointments and did not respond to calls.

"You abandoned the help of the police, took the law into your own hands and killed with a firearm."

Courtenay Griffiths QC, defending, said Mr Oxley said he would not answer calls when he did not know who the number belonged to.

He said: "Police were trying to get in touch with him with no luck."