SECRET footage of defence personnel training for a nuclear attack on Northern Ireland by the Soviet Union has come to light after more than 30 years.
The 1989 recording shows men and women of the Royal Observer Corps (ROC) calmly plotting simulated atomic blasts using computers, maps and telephones at its Lisburn bunker HQ.
It was given to Cold War buff Alastair McCann, who bought and restored an ROC bunker outside Portadown, one of more than 1,500 which were dotted across the United Kingdom.
"It's quite revealing because it shows people so relaxed and going about everything while training for something they hoped would never occur," Alastair told Sunday Life.
"At one point someone says something about 'four megaton' - that's a four-megaton nuclear bomb that has been dropped and the equivalent of four million tons of TNT.
"If a four-megaton bomb hit Belfast, you are talking about a blast wave that would not have stopped travelling in all directions until Culcavy, Larne, Ballywalter and places like that.
"The way they are just plotting this on a board, it all just comes down to facts and figures when you have been doing the training for so long."
Alastair believes the film may have been made to be shown to potential ROC recruits but someone realised some of what was captured was not meant for public consumption.
"There is equipment in that footage which was top secret, which shouldn't have been on video at all," said Alastair.
"There's a piece of equipment called AWDREY (Atomic Weapon Detection Recognition and Estimation of Yield), there were 12 of those across the UK and it was definitely top secret, and yet there it is in all its glory."
The ROC was a uniform civilian organisation formed just after the First World War to spot enemy aircraft, and proved themselves to be a vital part of the home defence forces during the Battle of Britain.
But it wasn't until the Cold War came into being that Northern Ireland, known as 31 Group, got its own ROC units, with the first recruited in 1954 and its first HQ set up in east Belfast.
"In 1959 they moved to their new headquarters inside Thiepval Barracks and from their underground bunker there they were in contact with 58 small nuclear bunkers across Northern Ireland," explained Alastair.
Although it was almost entirely made up of part-time members, it was a key arm of the UK's nuclear defence strategy until it was stood down in 1991.
It's job was to collect information about the location and power of nuclear "bursts" and the spread of radioactive fallout during an attack on the UK.
The ROC network was made up of regional bunkers, like the one in the footage, as well as the some 1,500 small monitoring posts housing two or three people.
Based on information made public after the fall of the Soviet Union, it's believed as many as 10 warheads were targeted on Northern Ireland, each one hundreds of times more powerful than the bombs dropped on Japan.
Exercises such as the one in the footage were conducted regularly, both internally among the British Armed Forces and civil authorities and right up to multi-national Nato-led mock wars with the USSR.
"The crew you see (in the film) is Crew 2 at the headquarters, usually made up of about 30 people, with the entire ensemble around 150 people, split up into three groups," explained Alastair.
"They took turns to operate the bunker but if they actually got the four-minute warning the headquarters would be locked and the crew there would be the one that stayed for the period of the nuclear exchange."
But just because they were in a semi-sunken bunker away from Belfast doesn't mean they were certain to survive a Russian strike on Northern Ireland.
"It would be far enough away from Belfast to survive but I imagine the Russians would have known enough about Thiepval Barracks to make it a target.
"So, more than likely the barracks would have been destroyed and if it was a direct hit, either an air burst or a ground burst, it would have been completely obliterated.
"If they had survived a war, they would have been opening a blast door onto a world that would have been starkly different to the one they had left four weeks before.
"The main places that would have been affected were Belfast, Lisburn, Armagh, Portadown, up around Derry/Londonderry would also have been hit."
Military sites on the Russian target list would have included RAF Aldergrove, the early warning radar station at RAF Bishops Court near Downpatrick and the US Navy communication station at Derry port. Another definite target was RAF Ballykelly, near Derry, which was one of the dispersal points for the V bomber nuclear force.
Atomic-armed Vulcans, Victors and Valiants would have been flown to the likes of Ballykelly before heading off to their targets behind the Iron Curtain.
"In terms of survival, you're talking at least 70-80% of the population of Northern Ireland either dead or dying," explained Alastair.
"When you put the pins on the map and figure the size of the warheads that would have been dropped, not much of Northern Ireland would have been missed.
"For those who managed to get away from the fallout, probably to the west of the country, what would have there been left after a nuclear war?
"Agriculture would have been decimated, cattle would have died and water contaminated, there would have been no power infrastructure or social order.
"A very bleak picture forms.
"The Royal Observer Corps training manual ends after the initial attack period - there's nothing after that page."
You can view the footage on Alastair's Facebook page 'Portadown Post' along with more images of the ROC and Cold War locations across Northern Ireland.