A man who killed a colleague in a frenzied knife attack has failed to convince top judges he was not in his right mind at the time.

David Squelch stabbed father-of-four James Wallington 14 times at the recycling centre in Tunbridge Wells, where they had worked together for several years.

Squelch, 50, of Paddock Wood, Tonbridge, admitted manslaughter, saying his responsibility was diminished because he was suffering from an "abnormality of mind".

However, he was found guilty of murder and jailed for life at Canterbury Crown Court in March last year.

He was ordered to serve at least 22 years behind bars before he can even apply for parole.

Squelch today challenged his murder conviction at the Court of Appeal, in London, with his lawyers arguing the trial judge misdirected the jury.

They said jurors may not have understood what they were being asked to decide, based on complex psychiatric evidence.

But his appeal was dismissed by three of the country's most senior judges, who said the instructions to the jury were clear and the conviction "safe".

The court heard Squelch attacked his 44-year-old colleague at the centre on the North Farm estate on 9 March 2015, after giving him a lift to work.

As Mr Wallington walked towards the entrance to collect the keys for the dustcart, he bent down to fasten his shoes.

At that point, Squelch ran up behind him and stabbed him 14 times in 15 seconds.

He then went to the office and told the foreman what he had done and said: "She's dead, now he's dead" - referring to his mother who had died the previous year.

Colleagues rushed to help Mr Wallington, but he died almost instantly.

The court heard the pair had worked together for a number of years, with Squelch driving a dustcart while Mr Wallington loaded it, and appeared to get on.

But Squelch started taking the murder weapon, a serrated hunting knife, to work after suffering a blackout in 2012 - for which he said he held the victim responsible.

He also punched Mr Wallington in 2014 for making a comment about his mother shortly after she died, although another colleague who witnessed the incident said the victim's remark was "innocuous" and that Squelch overreacted.

However, the pair appeared to have made up and they continued to work together with no further problems until the unprovoked attack.

Squelch's lawyers argued the judge didn't clearly instruct the jury what they had to decide in terms of his mental health in order to find him guilty of murder.

But, rejecting his appeal, Lord Justice Davis said the judge clearly spelled out the task for jurors.

Sitting with Mr Justice Jeremy Baker and Judge Sarah Munro QC, he added: "In our view, the issues were properly and clearly identified and the evidence was appropriately marshalled by reference to those issues."

Also dismissing a bid by Squelch to have his 22-year tariff cut, the judge concluded: "It may be that a sentence of 22 years as a minimum term was a severe one.

"However we are not persuaded that it was a manifestly excessive sentence in the circumstances."