Sergeant Alexander Blackman, a 39-year-old who has been in the marines since his 20s, loses fight to remain anonymous

The Royal Marine convicted of murdering a Taliban prisoner in Afghanistan can finally be named after he lost his year-long fight to remain anonymous.

He is Sergeant Alexander Wayne Blackman, a 39-year-old married man from the south of England who has been in the marines since his mid-20s and has served with distinction in Northern Ireland and Iraq.

Blackman, a member of 42 Commando, faces life imprisonment in a civilian jail when he is sentenced on Friday after becoming the first British serviceman since at least the second world war to be convicted of murder during an overseas deployment.

For more than 12 months Blackman has only been referred to as Marine A after the judge advocate general, Jeff Blackett, who oversees the court martial system, ruled that he would become a terrorist target if his identity was known.

But after a prolonged legal challenge by the Guardian and other media organisations, three of the most senior judges in the country, including the lord chief justice, Lord Thomas, have agreed that, in the interests of open justice, he should be named.

Marine A was finally named in the Lord Chief Justice's court in London. His name was read out by David Perry QC, the prosecutor in the court martial.

He told the court that Marine A was Sergeant Alexander Wayne Blackman and also gave out his service number: PO55242E.

Two other marines who were on the patrol with Marine A and were also charged with murder but cleared of the offence, still cannot be named. The court gave them permission to bring a judicial review on the issue.

The court refused to allow the video that captured the murder to be released after hearing that the government considered it an ideal recruiting tool for Islamist terror groups and could prompt a "lone wolf" to carry out attacks on British civilians or troops.

The ruling means that the full details of Blackman's career can be revealed for the first time.

After joining the corps 15 years ago his first taste of active service came in Northern Ireland. He quickly impressed and by the time of the September 11 terrorist attacks on the US, Blackman – known as Al – had been promoted to lance corporal and was in Oman taking part in Operation Swift Sword II, the largest single deployment of UK forces since the Gulf war. The presence of such a large force gave allied commanders a huge head-start as the fighting in Afghanistan got under way.

Over the next 10 years Blackman completed three tours of Iraq and two of Afghanistan. He took part in fierce fighting in Iraq as British forces helped overthrow Saddam Hussein and had many narrow escapes including one incident in which a vehicle he was in was badly damaged in a grenade attack. He completed an exemplary first tour of Afghanistan.

Blackman's final tour began when he was deployed to Helmand in March 2011 as part of Operation Herrick 14 – the name for the October 2011 - April 2012 phase of the British operation in Afghanistan – to help build schools, hospitals, roads and prepare Afghan forces for when they take full responsibility for security.

By then a sergeant, he was considered a safe pair of hands by his superiors, a physically imposing marine who always led from the front. During the court martial he said his approach was to keep things "as relaxed as possible" and claimed he wasn't a "shouty man".

He was put in a charge of a command post called Omar. The tour began quietly and Blackman was credited with building good relations with the local population. He was friendly with a local mullah who lived close to CP Omar and took part in good-natured shuras – meetings with community leaders and elders.

Blackman's tour heated up considerably at the end of the poppy harvesting season at which point the so called $10 Taliban – young men paid to fight for a few dollars a day – took up arms.

In May 2011, Blackman was hit particularly hard when a roadside bomb claimed the lives of two hugely well liked and respected marines, Lieutenant Ollie Augustin, 23, and Marine Sam Alexander, 28.

Blackman had mentored Augustin, a brave and brilliant young officer with the brightest of futures. "We had a good rapport," Blackman said. "He was developing into a very good officer."

Others were injured in the attack, including one man who lost a leg. Blackman and his fellow marines were outraged to see it hung from a tree as a gruesome trophy. "It's not a nice thing when you find out body parts have been displayed as a kind of trophy for the world to see," said Blackman.

The tour went from bad to worse. He has described life in Helmand as "frantic". By September – when the murder took place – the marines were stretched, partly because of the number of fatalities and injuries they had suffered. Blackman's team at Omar only had one day of rest every two or three weeks.

Marines that had been keen to taste action were now not so willing to put their lives on the line so close to the end of their tour and Blackman began to go out on almost every patrol.

"People are thinking about home; they are less keen to get shot at on a daily basis," he said. To make life even tougher, he was having do deal with the death of a close relative at home.

On 15 September 2011 when he and his patrol came face to face with the insurgent – who was suspected of carrying out a series of attacks on a neighbouring command post – he was stressed and jaded.

Typically he went and disarmed the injured Taliban fighter himself, taking a rifle and grenade off him to make sure – in his words, "there was no danger of him going bang and taking us with him".

Then, by his own admission, Blackman lost control and shot the prisoner, who had been badly wounded in a helicopter strike. The incident was captured on video. He was heard telling the dying man: "There you are, shuffle off this mortal coil, you cunt. It's nothing you wouldn't do to us."

Moments later, Blackman instructed colleagues: "Obviously this doesn't go anywhere fellas. I've just broken the Geneva convention."

Blackman has continued to insist he thought the man was already dead and he opened fire on a corpse in frustration. Asked about the way the man had been roughly treated and verbally abused by the marines before the shooting, he said: "They are the enemy; they are not nice people." But he said he was ashamed at his lapse in discipline.

Following the murder Blackman carried on with his duties as professionally as ever, not discussing what had happened with any of his colleagues. He left Helmand at the end of October, one of the last members of Herrick 14 to arrive home.

Back in the UK he was based in Folkestone, Kent, where he trained younger marines in the use of heavy weapons such as machine guns as they prepared for tours of Afghanistan. He had been selected for promotion to colour sergeant and his future seemed bright until a year after the shooting, when investigators came by chance on the footage of the incident, which had been captured on a head-camera worn against orders by one of Blackman's colleagues.

The Royal Marines have made it clear they will continue to support him. Major General Ed Davis, commandant general of the corps, said: "Our mantra of 'once a marine, always a marine' is not conditional."

His family has said he has their love and backing. But Blackman's military career is over, his anonymity has fallen away and he faces tough years behind bars in a civilian prison.

The Lord Chief Justice, Lord Thomas, heavily criticised the Ministry of Defence after it emerged the court's decision on the naming of the marines had been passed down though the chain of command to the men's commanding officer, who had told them of the result – before it was announced in court.

Thomas said such a breach was regarded with the "utmost seriousness" by the court and has demanded a written explanation of why it happened.

The MOD said: "The MOD acknowledges the lifting of the anonymity order in respect of Marine A. We presented our security concerns in open court, and an independent legal process has now concluded; we respect the decision of the court."