Two brothers face watching their critically-injured father die because their Jehovah's Witness mother refuses to give consent for a blood transfusion.
John Edwards, 57, was left fighting for his life after a car ploughed into him and is expected to have just days to live.
But despite doctors believing a transfusion is their best chance to save him, his wife Sheila refuses to give permission.
The Edwards are both devout Jehovah's Witnesses, a faith which bans its followers from receiving blood.
However, neither of their sons Jonathan, 36 and Tom, 29, share their beliefs.
A source close to the family said: 'Sheila is adamant that John must not have blood.
'She says giving him a transfusion would be like assaulting him - and he wouldn't want to live knowing he'd disobeyed his God.
'She's in a terrible state, constantly in tears at his bedside, but won't give in to requests from anyone.
'Her sons are both with her but her position hasn't budged.'
John suffered terrible injuries to his left side after he was knocked down on Tuesday night.
He was rushed to hospital where doctors fought desperately to save his life.
But 61-year-old Sheila refused to let her dying husband have blood, claiming he had signed a form stating he did not want a transfusion.
Despite being unable to produce the document, medics have had to abide by her wishes as she is his next of kin.
Last night the Edwards' lodger, who refused to give her name, said the family was devastated by what had happened.
The woman, who is also a Jehovah's Witness, told The Sun: 'There's a real question over whether John will pull through. The Kingdom Hall of Jehovah's Witnesses in Yeading, West London
'There's no doubt that non-Jehovah's Witnesses would automatically have a blood transfusion in the same circumstances.
'Sheila and the boys are all devastated.'
She went on to describe the accident, which happened just a short distance from the Edwards' house in Southall, West London.
She said: 'He was on foot and the car piled into him doing 60mph as it came around a corner. By chance, the police were on the same road when it took place. They breathalysed the driver and he was over the limit.
'Many of John's bones were broken and there was a lot of internal bleeding.'
'Both John and Sheila are Jehovah's Witnesses but neither of their sons are.
'They have been married around 40 years. Both were brought up as Jehovah's Witnesses.
'They are very devoted to the religion and John's a highly-respected elder, who sometimes gives talks to the congregation.
'John's also a keen sailor and has just returned from a competition with his brother. He's a happy, outgoing person. It makes this even more of a tragedy.'
John, a council worker, and Sheila, a retired languages teacher, attend the Northolt Kingdom Hall, in West London.
A spokesman for the Jehovah's Witnesses said: 'We express our sympathy towards the family.
'It is obviously a terrible tragedy, and we certainly feel for them, and understand that the hospital have been magnificent and doing all they can to provide care for this gentleman. We feel for them as well.
'The family have spoken in very glowing terms about the treatment and care they have received.'
He declined to discuss details of the case, because of patient confidentiality.
In November, it emerged Jehovah's Witness Emma Gough, had died after giving birth to twins because she refused to have a blood transfusion.
The 22-year-old, from Shrewsbury, Shrops, had a developed a blood clot but her husband Anthony, 24, and other relatives refused to let her have potentially life-saving treatment.
All the family are Jehovah's Witnesses.
The faith's ban on blood is based on the Bible passage from Acts 15 verses 19-21.
'Abstain from ... fornication and from what is strangled and from blood.'
There are around 130,000 Witnesses in the U.K.