Joan and John Stirland were traced by a criminal gang to their bungalow in Trusthorpe and gunned down after their address was handed over to the killers.

The fatal shootings were believed to in revenge for a murder committed by the couple's son Michael O'Brien.

The Stirlands had fled from their home in Nottingham after being targeted by gunmen. They reported a prowler hours before their deaths.

In 2006 gangster Colin Gunn, 40, of Bestwood, Nottingham was jailed for 35 years over the killings.

During his trial a court heard the crime boss ordered their murders as retaliation after O'Brien, murdered a friend of Gunn's nephew, Jamie Gunn.

The 27 year-old shot dead Mervyn Bradshaw, 22, outside The Sporting Chance pub in Nottingham, when he fired at the car he was driving.

Jamie Gunn, who was in the car at the time and was believed to have been the intended target, fell into a deep depression after his friend's death and his life spiralled downwards until he died from pneumonia on August 2. O'Brien was jailed for life for the murder.

The inquest in Lincoln heard members of the "criminal fraternity" believed Jamie Gunn was to have been the target of the initial shooting.

Mr Stirland, 55, and his 51 year-old wife were moved to the house in Trusthorpe eight months before they were killed in August 2004.

It was revealed a BT employee was subsequently convicted of illegally disclosing the information which led the killers to the Stirlands.

A jury were told they had to consider if Lincolnshire and Nottinghamshire police had failed to properly protect the Stirlands and if they caused or contributed to the couple's death.

Coroner Karon Monaghan QC told the jury at the start of the hearing: "This is not about investigating the immediate cause of the deaths of Mr and Mrs Stirland.

"We know how they died in the immediate sense. They were both shot a number of times.

"The purpose of this inquest is to consider whether any other persons contributed to their tragic deaths and look into the circumstances leading up to them.

"In particular you will have to consider whether there were failings on the part of the police which caused or contributed to the deaths.

"This is not a criminal trial, it is an investigation into matters leading up to the deaths.

"That will involve considering the steps taken by various police officers and forces in the lead up to the deaths and whether they properly dealt with intelligence pointing to a risk to Mr and Mrs Stirland.

"You will have to consider whether they did not take the steps they should have to protect them and whether police corruption played a part.

"You will also have to consider the involvement of BT, whose employee disclosed their address. An employee was subsequently found guilty of a criminal offence."

The inquest is being held at a secure courtroom at Lincoln Crown Court, with members of the public and media only allowed to view the proceedings on a video link in a building two miles away.

Michael O'Brien is being allowed to view the hearing on a separate TV link from his jail where he is now serving a life sentence.

The coroner told the hearing a number of police witnesses will be granted anonymity and will give evidence via video with their appearances disguised.

The inquest could last up to three weeks.