Suzanne Breen: Did spooks see Martin's bomb film?
If the BBC was able to find footage which could have sent McGuinness to jail was it really unknown to MI5?
He is rightly remembered as a peace-maker. A man who went places that nobody ever dreamed he would go.
Martin McGuinness, former republican revolutionary, didn't just meet the Queen on countless occasions - he did so with good grace, not through gritted teeth.
He was involved in secret dialogue with senior MI6 officer Michael Oatley which paved the way for the IRA ceasefire.
It was a remarkable turnaround because even when Sinn Fein began experiencing success at the polls, McGuinness had insisted it wasn't "winning elections and winning any amount of votes" that would secure Irish freedom "it will be the cutting edge of the IRA".
Now his portrait has pride of place in Stormont with that of his old adversary, Ian Paisley - the 'Chuckle Brothers' as the most unlikely allies became known.
In episode one of the BBC's Spotlight On The Troubles, A Secret History, reporter Darragh MacIntyre last week began to chart their journey from "dangerous radicals to elder statesmen".
Paisley (above) is accused of funding a UVF bomb. Just six months after the firebrand loyalist founded the DUP, Spotlight shows us footage of McGuinness.
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It's March 1972 and he's overseeing a bomb, wired to an alarm clock, being loaded into a car.
Thirty minutes later the device in the vehicle - identified by its number plate - explodes in the centre of Derry. We hear people screaming and see them running for cover.
A woman cries as the street is engulfed in smoke. On the day that the programme was aired, Sinn Fein's Foyle MP Elisha McCallion was outraged.
A New IRA bomb had been discovered by the PSNI in a car in Derry.
"Those responsible for leaving this device in such a built-up area put the whole local community at risk," she said.
"This could have caused serious injury or worse to anyone. Those responsible have once again shown their complete and total disregard for the local community.
"They have nothing to offer the people of Derry and need to call an end to these reckless and futile actions."
So what was McCallion's response to Spotlight's McGuinness car bomb revelation? Martin was "an amazing man who fought his whole life for what he thought was right. He was my friend, a hero and an inspiration to thousands".
The contrasting responses defy all logic. Because the dissidents' bomb didn't even explode, whereas McGuinness's did. People are visibly upset and scared. Clearly it was capable of causing injury or death. Does McCallion not believe it put people at risk and those behind it showed "disregard for the local community"?
There was also footage of McGuinness showing guns and bullets to children as young as eight. Both clips come from a film recorded by US journalists which was found by a Spotlight researcher.
So footage implicating an IRA leader - which could have put him behind bars for a very long time - has been around since 1972. The Provo campaign would continue for more than two decades.
If a Spotlight researcher could find the film, was it really unknown to the security services all these years?
McGuinness had been an Army Council member and was long regarded as the biggest threat to the British state. All its extensive resources would have been focussed on him.
I understand that further footage will be shown in the Spotlight series, and we will learn about the history of the film.
Was it locked away in a remote location or was it more openly and readily available?
If the latter, I suspect questions will be raised about how much the state really was at war with Martin McGuinness.