The man accused of murdering a Norfolk security guard insisted yesterday he had stabbed him by mistake as he tried to escape before the police arrived.

The man accused of murdering a Norfolk security guard insisted yesterday he had stabbed him by mistake as he tried to escape before the police arrived.

David Watson, 20, of Hackney, east London, was being held in an office at HMV in the Chapelfield Shopping Centre, Norwich, after being caught trying to steal a CD, when he tried to break free, stabbing and killing 30-year-old Paul Cavanagh.

At the time, he was carrying £1,400 of drugs and was receiving telephone threats by a drugs baron, known only as "Alvo", while he waited for the police to arrive.

"He said that if he didn't get his drugs back he was going to blow up my mum's house," Watson told Norwich Crown Court.

"If Alvo says he is going to do something, he does it. He is not the kind of man you argue with."

Watson said he had arrived in Norwich a few days before the incident of December 18. He had come to the city to deal crack cocaine and heroin in an attempt to pay off his own drugs debts which ran into tens of thousands of pounds. Having already sold £1,300 of drugs, he was carrying the remainder at the time of the HMV incident.

Giving evidence for the first time, Watson told the court he did not initially panic when he was caught shoplifting but became worried about the police arriving because he knew they would find the drugs and that Alvo was threatening to harm his family if he did not escape with the drugs.

During a protracted scuffle he had a number of chances to stab Mr Cavanagh but instead chose to try to push him off.

"I made a decision to pull the knife out of my bag and scare Mr Cavanagh with it so he would let me escape," he said. "I did not intend to harm him at any point."

It was only when the pair fell to the floor that the knife went into Mr Cavanagh, he claimed.

He said: "I got up and was covered in blood, it was spraying all over the place. I didn't know what happened."

Watson then fled, stabbing another security guard in the process. He claimed this was also an accident.

As he escaped, soaked in blood, along St Stephen's, Surrey Street and Queens Road, he was pursued by an off-duty special constable whom he also caught with the knife.

Watson denies murder, wounding with intent and attempting to wound with intent.

The case continues.