A Scots engineer has been detained indefinitely in a secure hospital after he admitted stabbing a relative of Arctic explorer Sir Ranulph Fiennes to death with a pair of scissors.

Nicholas Hunter, 37, launched a frenzied attack on 49 year-old James Fiennes at The Tapestry tapas bar in Mortlake, south London.

Hunter, originally from Uddingston, Lanarkshire, was seen acting bizarrely before the killing and was heard to say: 'The world is going to end tonight at midnight.'

The killer admitted manslaughter on the grounds of diminished responsibility after psychiatrists agreed he was mentally ill at the time of the attack on 22 April last year.

Hunter was also accused of threatening to kill another man, Thomas Olsen, during the same incident. The charge was left on the file.

Mr Fiennes, an IT consultant and entrepreneur, owned a flat opposite the scene and had been enjoying a quiet drink.

Police and paramedics were called at around 9pm but the victim died in hospital a few hours later at 2.20am on 23 April.

Mr Fiennes was a nephew of the peer Nathaniel Fiennes, a second cousin of Arctic explorer Sir Ranulph and a more distant cousin of the actors Ralph and Joseph Fiennes.

His wife and two children lived in Sherborne, Dorset.

Hunter launched the attack when Mr Fiennes walked over to ask how they knew each other after being called by name, the court heard.

Prosecutor Zoe Johnson QC said: "Mr Fiennes was acting in a dignified and polite fashion. Hunter said: 'James, I'm going to have to kill you.'"

Mr Olsen thought this was a "tasteless joke", the court heard. Hunter then emptied his pockets out on the table, including the scissors.

Miss Johnson said: "Mr Fiennes clearly thought this was a joke and in a spirit of humour made a gesture as if to unbutton his shirt and ask ''What are you going to do to me?''

"Then without provocation the defendant stabbed Mr Fiennes repeatedly."

Mr Olsen described the attack as "vicious... as if he was possessed."

Roy Fraser, a retired police officer who was in the bar with his wife, helped restrain Hunter at the scene.

Searches of his internet history revealed a small amount of transsexual pornography, the court heard.

Hunter was unable to explain why he stabbed Mr Fiennes but told one psychiatrist it was something to do with the impending end of the world.

He claimed he heard voices telling him he was a Glasgow hardman and saw images including Christ on the cross.

In a victim impact statement, Mr Fiennes' wife Caroline said: "The day I met James I knew I would marry him. I lived him then, I love him now and I will love him forever.

"He was my best friend, my soulmate, my rock or oak tree. Everything a good husband could be, James was.

"He was kind, considerate, funny, gentle, spiritual and intelligent. Above all he was loving.

"Everyone and anyone who knew James described him as a gentleman in every sense of the world."

Three psychiatrists agreed Hunter was suffering from schizo-affective disorder and recommended that he should be detained in hospital indefinitely under the Mental Health Act.

In a statement read out by his barrister Isabella Forshall QC, Hunter said: 'Words alone cannot express the sorrow I feel for the catastrophic situation I have caused to those affected. I think of them and I pray for them.

"I am so very sorry for the tragedy my actions have caused.' Miss Forshall said: "If this man hadn't become mentally ill he would have continued to live a conscientious, thoughtful and valuable life."

Rejecting the option of sending him to prison, judge Gerald Gordon said: "After careful consideration I have come to the conclusion that your responsibility for what you did at the time by reason of your mental illness was so substantially reduced and caused by your mental health that that is the right course.

"I should stress that I have taken into account both the ferocity of the attack and that the person you attacked was a total stranger. These two factors are totally consistent with the view I have formed as to your mental illness."

Hunter was detained 'without limit of time' under sections 37 and 41 of the Mental Health Act.