Former Labour spin doctor Alastair Campbell has revealed that Martin McGuinness helped him with his research into IRA operations for a new novel about a Provo gang attacking London.
Tony Blair's former right-hand man turned to the ex-IRA commander for advice as he prepared his book Saturday Bloody Saturday, which is set in the world of English football in the Seventies against the backdrop of a bombing onslaught in London.
Campbell credits McGuinness in the acknowledgements at the start of the novel, which he co-wrote with former Burnley footballer Paul Fletcher.
He said that he had no qualms about approaching Sinn Fein's Deputy First Minister for guidance about the IRA, who in the book plot to kill Ulster Secretary of State Merlyn Rees.
"Martin had a certain historical knowledge of the Troubles in Ireland, let's put it that way," said big Burnley fan Campbell, who has praised McGuinness down the years for encouraging republicans to move away from violence to seal the peace process.
He said that he asked the Derry republican, who died last March, specific questions about how the Provos went about their bombing business "checking one or two things for authenticity".
In particular, he consulted McGuinness about whether or not a terrorist in the book might be female.
He replied "yes", and a woman does indeed figure in Saturday Bloody Saturday as a member of a Provo active service unit.
Campbell, who sent the Sinn Fein leader a draft of the book to read, has already written in-depth in an earlier publication about the peace process and how pivotal a contribution McGuinness and Gerry Adams made to the Good Friday Agreement.
Though he's often been criticised by Tories and unionists for applauding McGuinness's role, Campbell has always said that he liked him from the start.
"I think at some point he had a real change of paths. I feel he genuinely made the journey of someone who was very much part of what he saw as the armed struggle to somebody who thought there were different ways of doing things," said Campbell. However, he added that he wasn't sure McGuinness ever regretted his violent past.
But after his death Campbell, who attended his funeral in Derry, described him as "a good guy who had been a bad guy".
Yesterday he told the Belfast Telegraph he was deeply concerned about how the Stormont Assembly was still stalled a year after McGuinness led Sinn Fein out of the Executive, not long before his passing.
Campbell said it was incumbent on all politicians here and in Britain to try to make Stormont work. "We had very many situations before Good Friday when we felt the whole process was going backwards. But with goodwill and focus you can get things back on track."
He warned that if that didn't happen soon, direct rule looked inevitable.
"And that would be a massive retrograde step," said Campbell, who has also been vociferous in his opposition to the Brexit vote, which he called a "catastrophically stupid decision".
The arch-Remainer has been campaigning for the result of the referendum to be overturned. He said the implications of Brexit and a hard border could be disastrous for Northern Ireland.
He added: "It's very worrying and I think Brexit has been consuming this Government 100%. I was absolutely appalled by the extent to which during the build-up to the referendum Northern Ireland barely figured in the debate."
He said McGuinness told him that when he met Prime Minister Theresa May for the first time, he was shocked at how low down the implications of Brexit on Northern Ireland had been in her list of priorities.
Returning to his new book's central theme, Campbell said that, like him, McGuinness was a football fan. He supported Derry City.
He recalled: "When we weren't directly involved in the peace negotiations 20 years ago, we used to have long chats about the game.
"He was a real fan, and he always kept me going about 'Buuuurnley', as he called us."
Ironically, a former Derry City footballer who later became a unionist MP featured in one of Campbell's first sorties into print.
Clifford Forsythe, the South Antrim MP, also played for Linfield and his exploits featured in a book that Campbell co-edited in 1994 about MPs and their football passions.
Football And The Commons People was launched at Westminster by Blackpool legend Sir Stanley Matthews, but Campbell's other claim to footballing fame is that he turned out in charity games alongside Pele and Maradona, names he loves to drop into conversations just to rile his co-writer Fletcher, who enjoys reminding Campbell that he played the game for real.
In their publication, Campbell and Fletcher also thank ex-Republic of Ireland star Johnny Giles and one-time Manchester United manager Tommy Docherty for their input into the football side of Saturday Bloody Saturday.
Some of the 14 books Campbell has penned during his writing career have dealt not only with his Downing Street days, but also with the depression that he has had to battle.
He said: "I'm currently making a TV documentary about depression, and the judgment of doctors and scientists I've talked to is that if you've had depression, you will always have it coming and going. I had a very bad bout just a few weeks ago. Lots of things help me with it - family and friends are the most important, as is writing.
"Marilyn Monroe once wrote a poem 'Think In Ink', and that is definitely what I do."
The seeds for the new book were sown several years ago when Campbell teamed up with Fletcher, who scored the goal of the decade in the Seventies with a breathtaking overhead kick against Don Revie's Leeds United.
He laughed: "People still talk about seeing that goal in the flesh. There must have been 140,000 Burnley fans at Elland Road that day."
Fletcher and Campbell have been friends for decades and it was as they travelled together to Turf Moor to watch Burnley's home games that they decided to work on the book.
The first draft had already been written by Fletcher, and Campbell widened the narrative to bring in politics and the IRA storyline, but it's clear he was happy to revisit the simpler, more innocent days of football in years gone by.
They were times when football fans could expect to bump into their team's players in the pub or cafe after games rather than reading about their multi-millionaire lifestyles of private jets and luxury cars.
Fletcher said he wanted his children and grandchildren to know what football was like in the Seventies.
Campbell said he wanted his children to appreciate just how difficult it was to come through the dark days of terror in Britain and Northern Ireland.
Campbell said Burnley fans like him had fond memories of footballing heroes who came from Northern Ireland like Jimmy McIlroy, Alex Elder, Sammy Todd, Billy Hamilton and Terry Cochrane.
"We had great scouts in Northern Ireland," said Campbell, who has denied that the new book is about Burnley.
He said the fictional team were made up of his and Fletcher's observations on a number of teams with the end result the tale of a struggling northern club desperate to win and what happens when they go to London, where the IRA active service unit are planning to cause mayhem as Britain heads for a general election. Fletcher said he remembered that teams were often wary of travelling to the capital.
"They were scary times with all the IRA bombs going off. You didn't know what was going to happen," he added.
Saturday Bloody Saturday by Alastair Campbell and Paul Fletcher is published by Orion Books and on sale now, £18.99