A Good Samaritan has described in vivid detail his tense stand-off with a knife-wielding terrorist accused of murdering Sir David Amess.

The veteran Conservative MP was stabbed to death in the Belfairs Methodist Church in Leigh-on-Sea while holding a constituency surgery on October 15 last year.

Born in Plaistow, the 69-year-old had served as the MP for Southend West since 1997.

Ali Harbi Ali, of Kentish Town, stands accused of his “cold and calculated murder” - a charge he denies.

The 26-year-old further denies preparing acts of terrorism.

Giving evidence to the ongoing trial at the Old Bailey, Darren King said he immediately became aware of the danger posed by Ali as the pair came face to face at the church.

Yesterday - Wednesday, March 23 - the unarmed witness told jurors that he rushed into the building from outside when he heard what had happened.

Mr King said he tried to “calm” Ali, who stood clutching a blood stained carving knife in one hand, while shouting to his “hysterical” sister on a phone held in the other.

Ham & High: Ali Harbi Ali is due to go on trial for the murder of Conservative MP Sir David Amess, who was stabbed to death in October last yearAli Harbi Ali is due to go on trial for the murder of Conservative MP Sir David Amess, who was stabbed to death in October last year (Image: PA Media)

In one exchange, recalled to police hours after the stabbing and captured on police video, Mr King said: “He (Ali) said: I want to be shot.

“I said: They (police) do that in America, not so much over here.”

Mr King said he also asked Ali why he wanted to die, and how his sister would feel if he did so.

“He said: I’m gonna' be a martyr, I’m gonna' die a hero.

“And I said: No, you’re just gonna be dead, mate.”

Mr King said he saw the MP's bloodied body “crumpled up on the floor” in a vestry room at the back of the church.

He tried to reason with the suspect so he could tend to Sir David, who he had known for years and had been due to meet that afternoon.

The witness said Ali also tried to justify his actions, which jurors previously heard centred around the government’s supposed bombing campaign in Syria.

Mr King said: “It was all on Syria, the Iraq war, the innocent people who died over there, he wants to kill David, all the MPs that voted for the bombing.

The witness told police he eventually persuaded Ali to step to one side so he could treat Sir David, but retreated the moment he heard police sirens.

The trial continues.