A man who was jailed for his part in Britain’s largest armed robbery was fighting for his life in hospital on Saturday after being shot in the neck and chest during a suspected gangland attempted hit.

Paul Allen, 41, was shot six times through a conservatory window on Thursday night at a house in Woodford Green, north-east London.

The Metropolitan police said they had arrested a 50-year-old man on suspicion of attempted murder and firearms offences. He remained in custody on Saturday afternoon.

“This investigation remains ongoing and officers continue to follow a number of lines of inquiry,” said DCI Nicky Arrowsmith. “We are still appealing for any witnesses or anyone who has information to come forward and speak to police.”

Officers, some of them armed, were called to a property at 11.10pm on Thursday following reports of a shooting.

A spokesman for comedian Russell Kane, who owns the house and had rented it to Allen, said: “Russell’s thoughts are with the victim and his family at this terrible time.”

According to the Daily Mirror, Allen was initially attended to by a private security guard named Luke, who was patrolling nearby. The former Coldstream Guard said: “There was a lady in the doorway screaming that her partner had been shot. I found him half on the stairs, half on the floor.

“There was another lady and I helped her in giving first aid by applying pressure to the wounds. I told the partner, who was holding a baby, to take the children upstairs and stay on the phone to the emergency services.”

Allen was convicted for his role in the 2006 Securitas raid in Tonbridge, Kent, during which a gang of men, including some dressed as police officers, stole £53m in cash from a depot.

The manager of the depot, Colin Dixon, and his family were kidnapped at gunpoint to force him to cooperate. The gang left behind £153m because they could not fit it into their getaway lorry.

Police later recovered £21m of the missing cash, but the remainder has never been found.

Allen, a cage fighter, fled to Morocco four days after the robbery with his share of the takings. He was subsequently extradited to the UK in January 2008 and sentenced to 18 years in prison, of which he served nine.

In August last year, the Crown Prosecution Service let Allen off repaying more than £1.23m, which was said to have been his proceeds from the robbery.