Lawyers for an SAS sniper jailed for illegal possession of a weapon will lodge their appeal today.
Sgt Danny Nightingale, from Crewe who served in Iraq and Afghanistan, was sentenced to 18 months in military detention after admitting possessing a prohibited firearm and ammunition.
The father-of-two is currently being held in the Military Corrective Training Centre in Colchester, Essex.
His lawyers will launch an appeal against his conviction and sentence at the Court of Appeal this afternoon, as well as applying for bail.
The case has sparked a political split after Attorney General Dominic Grieve yesterday turned down a request from Defence Secretary Philip Hammond to review whether proper consideration was given to whether the prosecution was in the public interest.
The move left Sgt Nightingale's wife Sally "disappointed" after Mr Hammond's request had given her "real hope" that her husband could be home for Christmas.
She said she hoped the Attorney General would at least consider reviewing any decision by the Service Prosecuting Authority to oppose the appeal and seek a re-trial if her husband's conviction was quashed.
Although the Ministry of Defence (MoD) is unable to intervene directly in the legal case, it is understood that Mr Hammond's personal view is that it is in the public interest for any appeal to be heard as a matter of urgency.
David Cameron was said to be sympathetic to Sgt Nightingale and his family but his official spokesman said: "This is a case where due process has to be followed."
Sgt Nightingale pleaded guilty at court martial 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 for the funeral of two friends killed in action. He also admitted possessing ammunition.
The court heard that the gun was a gift from Iraqi soldiers he had been helping to train but Sgt Nightingale, who had suffered medical problems affecting his memory, said he did not remember having it.
His father, Humphrey Nightingale, said his son pleaded guilty in the expectation he would be dealt with leniently.
MPs last night discussed the case in the Commons, saying prosecutors should not oppose an appeal by Sgt Nightingale.
Julian Brazier, a former member of the Territorial SAS who secured the adjournment debate on the issue, said Sgt Nightingale had "risked his life for his country again and again".
Mr Brazier asked Solicitor-General Oliver Heald: "I urge you to review the service interest test in this case and allow the planned appeal to go through unopposed."
Tory MP Patrick Mercer, a former soldier who has sat on court martial panels, said he respected the military justice system but the treatment of Sgt Nightingale had not been in the army's interests and could affect morale in the armed forces.
Sgt Nightingale's lawyers yesterday said they remained confident in the prospects of an appeal.
Simon McKay said although the Attorney General declined to intervene, he was glad the case had been brought to his attention.
He added: "I am working with William Clegg QC, one of the most experienced criminal silks in the country, and there is a strong degree of confidence."