Veteran Conservative MP Amess was stabbed to death at a Methodist church in Leigh-on-Sea in southeast England in October.

Ali Harbi Ali, 26, from north London, was arrested at the scene and has pleaded not guilty to murder and to preparing acts of terrorism.

On the opening day of his trial at the Old Bailey court in central London, prosecutor Tom Little told jurors that Ali was undoubtedly responsible for the “cold and calculated murder”.

“This was nothing less than an assassination for terrorist purposes,” he said, noting it was “carried out because of a warped and twisted and violent ideology.

“It was a murder carried out by that young man (Ali) who for many years had been planning just such an attack and who was, and is, a committed, fanatical, radicalised Islamist terrorist.”

Little said Ali had been determined to carry out a terror attack “for a number of years”, and had bought the knife allegedly used to kill the lawmaker in 2016.

He had researched and planned potential attacks on the Houses of Parliament and other MPs, including targeting the higher profile senior minister Michael Gove, the prosecutor added.

The 26-year-old defendant appeared in the dock wearing a black robe and black-rimmed glasses.

The killing of Amess, the second of a British MP within five years, shocked the country and led to calls for better security for elected representatives.

In 2016, a right-wing extremist who shouted “Britain first” shot and stabbed Labour MP Jo Cox to death in the febrile run-up to the Brexit referendum.

The Old Bailey jury was told that Ali had tricked his way into getting an appointment with Amess by claiming he was moving into the constituency.

The defendant had appeared “relaxed and chatty” moments before he “brutally” stabbed the MP in a “vicious and frenzied attack” shortly after midday on October 15, Little said.

Afterwards, Ali waved the bloody knife around and said “I killed him, I killed him” while threatening those present to stay away from him, he added.

“I want him dead. I want every parliament minister who signed up for the bombing of Syria, who agreed to the Iraqi war to die,” he allegedly added.