Campaign to free Marine A - and how he spends his day in prison for killing a Taliban insurgent

Sgt Alexander Blackman - known as Marine A during his court martial - must serve at least eight years behind bars, but tens of thousands of supporters are working tirelessly to get his conviction quashed.

This week we look at how he is spending his time in prison and at some of the efforts to secure his release.

*WHILE his family, friends and supporters are pulling out all the stops in a bid to get his murder conviction quashed, Blackman has slipped into the sort of disciplined routine you'd expect of a military man.

He works in the library in the mornings and afternoons and pushes himself through tough gym sessions five times a week, as well as a weekly run in the grounds of HMP Erlestoke, in Wiltshire.

He has also completed a course to qualify as a volleyball umpire, is taking his level three fitness instructor exams and is studying for an Open University degree in geography and environmental science.

His wife, Claire, who visits every week, said: "The military lifestyle has prepared him better than many of the other lads in prison.

"He's used to and is comfortable with having a regime and discipline in his life.

"He doesn't object to being up at a certain time, being by his bed for roll-call, whereas lots of the lads in prison object to doing anything that is asked of them.

"In the library, he issues books and DVDs, stocks books and places order.

"At first the other staff would keep the newspapers behind the desk if there was a story about Al.

"They all know who he is, but they don't make a fuss about it.

"New lads come in and pat him on the shoulder and say, 'You're that soldier, aren't you?' He's given up correcting them that he's a Royal Marine.

"He's always been fit, but he sets himself ridiculous challenges on the rowing machines and is even fitter now."

Blackman, who had been in the Marines for 15 years before the incident in Helmand Province, Afghanistan in 2011, has no intention of causing trouble in prison.

During a disturbance in HMP Erlestoke in the summer, a number of fellow prisoners on his wing went into his cell to get a better view and began shouting encouragement to the rioters.

Blackman told the Daily Mail: "I asked them to stop because if they were seen at my window, I would get the blame and you can get another ten years on top of your sentence for taking part in a riot.

"There will always be some here who have an 'us and them' approach to the prison authorities and life inside.

"But mine is strictly 'me and me' or 'me and Claire'.

"Our future is the most important thing and I don't want to jeopardise it any more than it has been already. Claire has suffered enough already."

Meanwhile, hundreds of thousands of people who feel Blackman should never have been accused of murder let along found guilty, are doing everything in their power to persuade the authorities to overturn his conviction.

A 100,000-signature petition sparked a debate in the House of Commons, while a crowd of 2,700 gathered in Parliament Square last month to peacefully show their support.

Daily Mail readers have donated £804,000 to help fund the legal team working to secure Blackman's freedom.

Military bosses and politicians are among those outraged that a military man should be accused of murder after being sent to fight for his country and Day of the Jackal author Frederick Forsyth has also thrown himself into the campaign.

"We wouldn't be where we are today without him and everyone else, and I can't fault the Daily Mail for its support and pro-active campaign," said Mrs Blackman.

"It must be quite surreal for Al. He's distanced from it physically, but it's very much about him and his case.

"He's incredibly grateful for the support and a bit overwhelmed - he's actually a shy, retiring type.

"We can't thank people enough. All the support gives us so much strength. We just feel like the whole country's behind us.

"It will be really frustrating if we have to wait the full eight years.

"It's the first time in my life that I've been wishing time away.

"If a friend says, 'It's Christmas soon', I say, 'OK, how long is it till Easter?'

"We just want the time to pass quickly. We're both of the mindset that if we work on the basis that he'll have to do the full eight years, then anything else that happens is a bonus."

Mrs Blackman speaks to her husband on the phone every day and has never given a moment's thought to moving on without him.

She said: "Al has never said, 'Get on with your life without me'.

"Everything he works towards is to be able to come home to spend his time with me.

"Everything I do is to get him home so we can be together.

"Some people say, 'How can you stay with him? How can you wait?'

"It isn't something I can comprehend. I made my marriage vows and I meant them."

Despite the widespread support, there will always be a few who believe Blackman deserves to be in jail.

His wife said: "I've had conversations with people who say, 'Murder is murder' and one or two letters saying the same.

"They are entitled to their opinion."

But Mrs Blackman has never felt the issue had put her in any danger.

She added: "The police were mindful of that from when the trial was announced.

"I've had security briefings and checks of my home.

"It would be foolish not to be mindful of that, but I've not experienced any cause for concern."