A dustman, who has admitted killing a workmate in a frenzied knife attack, did it because he was suffering from paranoid personality disorder, a jury has been told.

David Squelch plunged the knife into James Wallington 14 times within seconds of arriving to work last March.

The 49-year-old former soldier, from Maidstone Road, Paddock Wood, has admitted manslaughter but denies murder.

Dr Norman Lockhart – one of three psychiatrists who has given evidence at the trial - told Canterbury Crown Court that at the time of carrying out the killing, Squelch had “snapped”.

He told how he had questioned Squelch about the car journey to work at Cory Environmental Recycling Centre in Tunbridge Wells which the two had made that morning.

“He told me that it was just a normal conversation about work. But he said he felt angry even though there had been no harsh words said in the car.

“That was as a result of something that happened the previous week when the victim had made some remark about his mother but he didn’t tell me what had been said.”

The psychiatrist added that Squelch’s condition meant he had a suspicious nature and was someone “who tended to misinterpret what were quite innocent remarks”.

He said Squelch would think the "sometimes trivial" remarks were aimed at demeaning or humiliating him and he would hold a grudge and react angrily.

Dr Lockhart said he concluded that Squelch – who in 1995 had confessed to police he had carried out a bank robbery – met six out of seven diagnostic criteria for someone with PPD.

Squelch told the psychiatrist he had been carrying a hunting knife in his van because of an incident years earlier when he suffered a “black out” which he blamed Mr Wallington for.

He told the doctor he had been sitting in the cab of the dustcart and felt Mr Wallington was staring at him, “which he took as an act in some way done to victimise him”.

"The anger and bitterness built up to a point that the very firm control he had kept over many years finally snapped" - Dr Norman Lockhart

Dr Lockhart added: “People who suffer with this disorder view the world as a very unsafe place and they feel a sense of insecurity. The intensity of the anger builds up because of the unresolved grievance.

“That anger overcomes the person but the intensity of that anger isn’t related to anything which has just happened at that point.

“It is the accumulation of events for something which has not been forgotten and for which grudges are held.

“In my opinion the anger and bitterness built up to a point that the very firm control he had kept over many years finally snapped.”

Defence barrister James Turner QC asked: “Did he make a rational choice on March 9?”

The doctor replied: “In my opinion, no. The exercise of control of his anger had resulted in the accumulation of grievance to the point which the intensity was such that he could no longer control it.”

Prosecutor William Hughes had told the jury earlier that the two men had been a team at the depot for two years and had got on well.

They had arrived for work in Squelch’s car in North Farm Lane just seven seconds before the stabbing.

The incident was caught on CCTV. Footage shown to the jury showed Mr Wallington walking towards the barrier at the depot, and Squelch running up behind him and launching the 20-second attack.

“Mr Wallington does little to defend himself and the reason is that Mr Squelch wasn’t punching but stabbing him with a serrated Bear Grylls hunting knife," he added.

The jury heard colleagues performed CPR as paramedics and the air ambulance crew raced to the compound – but Mr Wallington died within 50 minutes.

The trial continues.