A man accused of slashing another man's neck in a bar said he felt threatened and believed he would be attacked.

Shane O'Brien stabbed 21-year-old Josh Hanson, from Kingsbury, in an act of "pitiless savagery" at RE Bar in Eastcote in October 2015 before going on the run for three years, the Old Bailey has heard.

Today, O’Brien told the court he believed his victim was "possibly" armed after seeing him "passed something shiny".

In cross-examination, prosecutor Mark Heywood asked: "At the time did you see Mr Hanson with a weapon?"

O'Brien replied: "I didn't see him obviously with a weapon.

"He possibly could have had a weapon and I had seen him passed something shiny.

"In my mind when I went up to approach him I felt under threat and possibly he could have had a weapon."

Jurors have seen a video showing the moment O'Brien slashes the council worker in front of his girlfriend shortly after 1am after the bar lights came on for closing time, inflicting a 37cm wound from his left ear to right chest.

As footage around three minutes before the attack was played, Mr Heywood asks: "There is no hostility is there? Where was the hostility at this stage?"

O'Brien said: "That bar is very small. Just body language can create an atmosphere."

Mr Heywood said: "It can if you're looking for it, Mr O'Brien."

O'Brien has told the court he wanted to "pretend to attack" Mr Hanson with a knife bought from B&Q earlier that day to "scare him", adding: "From the bottom of my heart I did not mean to touch him with that blade."

Asked by defence lawyer Graham Trembath yesterday to explain what happened, O’Brien, 31, said he had sat down with three friends near council worker Mr Hanson and his group before it became apparent "they wasn't happy with us sitting at that table".

He had said: "Amongst our little crowd everybody agreed the situation seemed hostile. It felt like they judged us as soon as we sat down.

"After, it became obvious the problem was with me in particular.

"Josh in particular started being very aggressive, by his facial expressions. He was making very aggressive body language, staring straight into my eyes.

"He was the instigator of the whole thing. He was raring to go. Personally I felt like he was ready to attack me."

CCTV images played in court yesterday showed the moment Mr Hanson, a former Moss Hall School pupil, arrived at the bar at around 12.45am on Sunday October 11, with footage also showing the pair first passing each other several minutes later.

O'Brien had told the court on Monday that after standing to leave the bar at closing time he approached Mr Hanson: "I said something along the lines of 'what's your problem? Leave me alone'.

"He was smirking, in a sarcastic action. Still keeping up the persona.

"When I stood up I didn't have a plan to do anything. When I approached him in that split second, that moment froze.

"When I made that action I didn't mean it to connect with him in any way.

"I wanted to scare him off. To pretend to attack him to scare him. Honestly, from the bottom of my heart I did not mean to touch him with that blade.

"I did what I did because I felt like I was about to be attacked. I genuinely felt threatened."

Jurors have heard O'Brien accepts he used the blade to cause Mr Hanson's death but says he is not "criminally responsible" because he did not mean to kill him.

The trial continues.