A gun enthusiast who became infatuated with a woman shot her neighbour after becoming embroiled in a bitter dispute, a court was told.

Thomas Hughes, 40, allegedly blasted 22-year-old Krystal Hart in the head at point blank range on the doorstep of her Battersea home.

She died instantly after opening the door to her killer at 11am on Good Friday, April 6 last year, the Old Bailey heard.

Miss Hart had become involved in an ugly feud with neighbour Angela Brewer, who lived in the flat below her in a converted terraced house in Belleville Road.

Miss Brewer's long-term friend Hughes became involved on the day of the killing when Miss Hart's boyfriend David Sivete noted down his car number plate, said prosecutor Aftab Jafferjee.

He said the incident, an hour before the shooting, sparked an "instant, furious obsession."

"It was the catalyst for a catastrophic event which can only be described as an execution," he told the court.

"The result was this defendant going to his own home, which was nearby, and collecting a gun and returning to shoot Krystal Hart at point-blank range in the head as she stood on her own doorway and killing her instantly.

"This defendant denies it was he who shot her."

Miss Brewer, 53, was 'almost obsessive' about noise from the upstairs flat and had reported Miss Hart to the police, housing association, council and county court.

She would tell "anyone who would listen how impossible her life was", said the prosecutor, and could be described as the "proverbial neighbour from hell".

At the time of the killing, the local authority was compiling a file against her in a bid to secure an antisocial behaviour order.

Both she and Miss Hart had installed their own CCTV cameras trained on the each other's front doors as the dispute continued.

Miss Brewer had made threats at her younger neighbour and claimed anyone messing with me, I will get them killed'.

She had also made utterances about shooting' but was known to be 'all talk', jurors heard.

Hughes lived at home with his mum and had known Miss Brewer for three years.

He had an interest in guns, some of which he kept at home, and had become 'infatuated' with his friend.

"He did what he did precisely because of the underlying animosity and empathising with his friend," the prosecutor continued.

"A woman he was not obsessed with, but almost certainly infatuated with, even though he recognised Angela Brewer's failings."

He had been heard to tell people Miss Brewer was 'a mad old woman' but also told her: 'I will do anything for you. I would cut off my arm or leg if I had to.' Mr Jafferjee said Sivete was Hughes' primary target but it was Krystal Hart who opened the door and was shot.

Miss Brewer will give evidence during the trial.

Hughes, of Stonells Road, Battersea, denies murder and possession of a firearm with intent.

The trial continues.