When naval intelligence officer Ian Fleming set up a secret commando unit during World War II, among those handpicked for duty was Theo Ionides - my grandfather. His band of real-life James Bonds helped change the course of the war.
My grandfather was - at 39 - already an old man by military standards when he joined Royal Navy Volunteer Reserve in the early years of World War II. So it was perfectly plausible when he told my grandmother that they kept him well away from the front line, out of harm's way.
His story was that the Admiralty had got him doing dull, technical stuff, poking around in the innards of new torpedoes and mines. But that couldn't be further from the truth, as my family discovered just a couple of years ago.
In fact my grandfather, Lieutenant Theo "Rusty" Ionides, had been handpicked by none other than Ian Fleming to be part of the Bond creator's top secret crack team of commandos. He'd been trained in all the tricks of intelligence gathering, ready to be sent into battle ahead of the advancing troops at D-Day.
The story of 30 Assault Unit, as the commandos were known, is a tale of audacious derring-do. 30AU was Commander Ian Fleming's greatest single contribution to the war effort and became the real-life inspiration for his most famous creation, James Bond.
It all began in the now famous Room 39 of the Old Admiralty Building. This oak panelled office overlooking Horse Guard's Parade and out across to the garden of 10 Downing Street is where Fleming worked as a volunteer officer in naval intelligence throughout WWII.
It is a sterile place now, used for training and lined with white Formica-topped tables and a large whiteboard. According to Nick Rankin, a historian who has written the definitive history of the unit - Ian Fleming's Commandos: The Story of 30 Assault Unit in WWII - it was very different place 70 years ago. Bakelite phones would have been ringing incessantly, filing cabinets crashing open, the fire crackling in the hearth.
Then, Room 39 was packed with men, all smoking like chimneys. These were the cream of naval intelligence, tasked with using their guile and imagination to come up with novel ways of confounding the Germans.
Overseeing them from the adjoining office was the formidable Admiral John Godfrey, their boss and the inspiration for M in the James Bond novels.
And back at the start of the war, the main preoccupation of his team was how to address a key British weakness - the fact that the Germans led the Allies in all sorts of technologies - encryption, rockets, submarines, torpedoes, mines and much more.
In 1942, Fleming proposed a simple solution - steal it.
His plan is outlined in a succinct single-page memo, hammered out on a typewriter in Room 39. It is headed Proposal for Naval Intelligence Commando Unit and right from the first paragraph it is clear that - in the spirit of 30AU - the idea itself is stolen.
"One of the most outstanding innovations in German intelligence is the creation by the German NID [Naval Intelligence Division] of special intelligence 'Commandos'... their duty is to capture documents, cyphers [sic] etc before these can be destroyed by the defenders," writes Fleming, under his codename F. "I submit that we would do well to consider organising such a 'Commando'."
Godfrey's response is plain to see. "Yes," he has scrawled in large letters at the foot of the page. "Most decidedly."
30AU was born.
In essence what Fleming was proposing was a team of authorised thieves and looters - mavericks who would operate ahead of the forward troops and who were instructed to do whatever necessary to capture enemy intelligence, equipment or personnel.
The men of 30AU were trained in all the key commando skills - hand-to-hand combat, booby traps and explosives. Many learned to parachute, handle small boats or dive as frogmen. They learned how to break and enter, how to pick locks and crack - or blow - safes (and were required to sign a document promising not to use these new skills in civilian life).
But despite their considerable skills, the first foray of A Commando, as it was known then, was not a success. It came in August 1942 when they were part of the disastrous Allied assault on Dieppe. Fleming was there in person to witness the disaster - his only experience of battle.
Paul McGrath is one of the last survivors of that raid. He's now 90 but still has a ramrod straight back. His clear, bright eyes sparkle and his face lights up as he recalls his adventures with the unit. Except when I ask about Dieppe.
He remembers sitting hunched on the deck of the destroyer taking him and his comrades into battle. As they approached Dieppe, the German gunners, dug into emplacements in the cliffs, opened up with everything they had. A large shell exploded just 20ft (6m) from where he sat.
More than 70 years on from that day, McGrath searches for words to describe the abject terror that gripped him as the blast wave hit. He says he was "frozen on deck, completely paralysed".
"I was petrified with such a terror it stunned my mind," he has written. "I lay on the deck with a sort of premature rigor mortis, immobilised by the awful thought of an immediate and terrible death."
That, he says, is when what had been for him the game of war turned deadly serious. "The sods were actually trying to kill ME!"
When the landing craft became lodged on a submerged object just a few metres from the beach, he realised the game was up. Machine and cannon fire rained down from the cliffs as McGrath and the other commandos stripped off their kit, throwing aside their weapons.
Those that could swim dived off the boat and swam for their lives through a sea foaming with bullets. McGrath - not a strong swimmer - says he was beginning to go under when the smokescreen cleared and he was spotted by a small Allied boat which dragged him aboard. It was the first of many close calls for McGrath.
But almost 1,000 other men had no such luck. They died in the raid at Dieppe, which most military scholars regard as an unmitigated disaster. Fleming's commandos came back empty-handed. They hadn't even stepped ashore.
Yet back at the Admiralty, Godfrey had not lost faith. Replacements were recruited for the lost men and the team was prepared for Operation Torch, the assault on North Africa.
Here Fleming's Red Indians, as he once called them, were more successful. They were deployed again during the offensives in Malta, Sicily and the Italian mainland during 1943. This rag-tag collection of marines and intelligence experts seized codes, secret documents and all sorts of novel German kit including an Enigma machine. They even bagged an Italian admiral.
So when the Allies were planning the greatest offensive of them all, Operation Overlord - code name for the Battle of Normandy, starting with D-Day - top brass wanted 30 Commando, or 30AU as the troop had been renamed, to be part of it.
That meant more personnel so, while 30AU was at work in the Mediterranean, back in Britain the men of Room 39 were busy recruiting. At a new base in Littlehampton, West Sussex, this new cadre was being trained in the essential commando skills. Among them was my grandfather.
A key condition of joining the unit was absolute secrecy. All members had to sign the Official Secrets Act. So my grandfather told my grandmother nothing about his new role. She knew he had been in training before he visited London in March 1944, but not what his role was to be.
The last pictures of him were taken on that visit when he took his two daughters - my mother Penelope and her sister Anthea - to Hampton Court Palace on a spring afternoon.
The family only discovered his involvement a couple of years ago, thanks to a coincidence.
My cousin Alexander is an eye doctor at Moorfields Eye Hospital in London and the only one of the family to carry my mother's maiden name, Ionides.
One day a patient asked him a startling question.
"Ionides is an unusual name," he said. "Was your grandfather called Theo?"
"Yes," replied Alexander.
"Did he fight in World War II?"
"Yes," he answered again.
Then came the real eye-opener.
"Did you know he was handpicked to be part of a top secret commando unit set up by Ian Fleming?"
The answer to that question was a resounding no. This amateur historian had opened a chapter of family history that we had no idea existed.
My grandfather was born in March 1900, the middle child of a well-to-do family of Greek origin that had fallen on relatively hard times.
We've got the letters he wrote from school to his parents. It is clear he was very excited by WWI and eager to join up. As soon as he was 18 he joined the Royal Navy but during training, the war ended and Midshipman Ionides didn't - to his disappointment - ever see action.
He left the navy shortly afterwards and secured a place at Oxford in the university's new discipline, engineering. He never finished his degree - we don't know why - but his engineering expertise was to find a useful role in the next war.
Theo never really settled down. In the early 1920s he went to work for the Greek merchant company Ralli Brothers in India. His sister Elfrieda apparently told him the parties were fantastic.
But Ralli Brothers did not prosper and the company's Indian operations were closed in 1930. He returned home to London and, with Britain in the grip of the Great Depression, found himself unemployed. He finally managed to get work at a dry cleaning firm. This was a brand new technology in Britain, and probably more glamorous than it seems now.
Nevertheless, when war was declared in September 1939, he was very eager to sign up.
Having served as a midshipman, the obvious place for him was the navy. According to family legend, he had quite a struggle to persuade them that a 39-year-old could be useful, even lying about his age to get in. It was his engineering skill that did it.
He was finally offered a commission as a 2nd Lieutenant in the Royal Navy Volunteer Reserve.
My grandfather became an expert in torpedoes and mines. He was deft at defusing the things, but also had an eye for technology, so was sent abroad to try and scout out new weapons.
It seems he caught Fleming's eye when he brought the innards of some particularly intriguing new torpedo back to the Admiralty from Sicily.
After a couple of months of commando training in Littlehampton, he was bundled on to a boat to join the greatest sea-borne invasion force in history - the D-Day landings.
Unfortunately he was not to play a big role in what happened next.
I've managed to track down three surviving veterans of the unit, men who were with him on that journey. None knew my grandfather in life, but 70 years on, all three remember his death very vividly indeed.
Four days after D-Day, the landing on Utah beach was easy. "Like stepping ashore at Margate," recalls Pte Bill Marshall.
The problems came after 30AU bedded down for the night in a field a few miles inland. The veterans all remember the German plane that suddenly appeared over the hedgerow and the bombs it dropped - a new kind of anti-personnel weapon, they were later to discover.
Almost 70 years on, I sat with each of them as they described how the shower of bomblets it released exploded, sending spinning scythes of shrapnel hurtling out over the field.
"There was a kind of humming and fluttering like butterflies," says Marshall, clearly still intrigued by the sound after all these years.
But there was nothing gentle about this weapon. Twenty-two men were injured, three fatally - one of whom was my grandfather.
Allen Royle - "Bon" Royle as he became known in the unit - tells me how he walked over to where the injured men were lying, many screaming in agony.
"I remember the medical orderly opening the buttons on your grandfather's shirt. I don't know why I remember it so well, but I do. His shirt was soaked in arterial blood," he tells me.
"The orderly opened it up and I could see his chest and the entry wound where the shrapnel went in - I think it was a bomb fin. He would have died immediately, I'm sure of that."
He is matter of fact as he says this. It is clear that Royle saw many horrific things during the war.
I'm surprised now how unmoved I am as he describes my grandfather's death. I suppose I am insulated from the horror by seven decades, and by the journalist in me who is keen to hear the facts - excited by these old men's stories of wartime derring-do.
It is a different story in Normandy.
Bon Royle and his son Nick made the journey back to Utah beach and retraced the unit's movements. Nick Royle texted me a photo of the map of Normandy they'd used. He'd circled a field in pencil.
A few weeks later a farmer leads me towards the spot marked on the map. He had no idea that any English soldiers had died there. Paul Woodage, the military historian who accompanies me, isn't surprised. So many people died in the days after D-Day, no-one knows where all of them fell.
We continue through the mud towards a gate into another field.
"I'm not superstitious, but lots of people just know when they are in the right place," Woodage suggests.
I'm not superstitious either, but he's right. We walk through a gate and into the field and it just feels right - this is where it happened. All the glamour and excitement of the connection with Fleming and James Bond evaporates.
That's when I remember the famous Rupert Brooke poem about the nobility of dying for your country and the "corner of a foreign field that will be forever England".
I am proud of my grandfather and I believe the cause he and the others who died there were fighting for was noble. But the fact is that standing in the field where my grandfather died doesn't make the pain of loss my mother has carried all her life any more meaningful. If anything it makes it less so.
This place will never be forever England, I think. This is a miserable place for anyone's life to end.
I turn and trudge away, feeling hollow.
But as I walk I begin to wonder if I'm being hasty. I have no doubt that he would have been very proud of what 30AU went on to achieve.
His comrades seized the entire German naval archive, later used as evidence in the Nuremberg trials. They captured top-secret German technology and some of the scientists behind it, and even played a part in the capture of Hitler's successor Admiral Karl Doenitz, thus sealing the end of the Third Reich.
Of course this is just some corner of a foreign field, but that's not the point. The field doesn't matter. What's important is the corners of all our hearts where the memories of the dead and what they achieved live on.
Justin Rowlatt's films on 30AU will be broadcast on The One Show on BBC One, 6 and 7 March, at 19:00 GMT