An SAS sniper jailed for illegally possessing a gun has become "gaunt" and is "struggling with being locked up for 16 hours a day", his wife said today.
Sally Nightingale met her husband Sergeant Danny Nightingale for the first time since he was sentenced almost two weeks ago.
The serviceman, who served in Iraq and Afghanistan, was sentenced to 18 months in military detention by a court martial after pleading guilty to possession of a prohibited firearm and ammunition.
After the visit at the Military Corrective Training Centre in Colchester, Mrs Nightingale said: "I saw my husband Danny at the military prison today. He was trained to deal with being detained by the enemy - it is impossible for him to understand how he has found himself detained at the hands of the country he has served so loyally for over 17 years."
Mrs Nightingale, accompanied by Sergeant Nightingale's father Humphrey, said her husband is finding his situation difficult, but is "humbled" by the public's support.
She said: "Danny is gaunt and as someone who has enjoyed an active and outdoor life, is struggling with being locked up for 16 hours a day.
"However he is being treated professionally and with compassion by staff and making a contribution to the training of other detainees.
"My husband is overwhelmed by the public support. He has received letters from members of the public and when told of the level of support he has is genuinely humbled."
The case has sparked controversy, with supporters claiming the father-of-two, who has served for 17 years, including 11 with the SAS, has been betrayed.
Mrs Nightingale has written to the Prime Minister asking to meet to discuss the "injustice" of her husband's sentence.
In a letter seen by the Sunday Telegraph, Mrs Nightingale asked Cameron not to "ignore" her family "in the hour of our greatest need", and urged him to intervene.
"I would like to speak to you face-to-face and explain in person why this sentence is such an injustice," she said.
"Prime Minister, you can help my husband and his family. Your intervention can end his detention."
Sgt Nightingale pleaded guilty to illegally possessing a 9mm Glock pistol which had been packed up and returned to him by colleagues after he had to leave Iraq in a hurry to help organise the funeral of two friends killed in action. He also admitted possessing ammunition.
The case is to be debated by MPs on Tuesday evening, with four special forces veterans, including the former commanding officer of the SAS, having written an open letter to Mr Cameron, claiming Sgt Nightingale was "the victim of a monstrous miscarriage of justice".
The court martial heard that the gun was a gift from Iraqi soldiers he had been helping to train, but the father-of-two, who had suffered medical problems affecting his memory, said he did not remember having it.