Sir Christopher Lee, who died last month aged 93, knew how to play a part. One of the consummate actors of his generation, whose career spanned nearly seven decades, his versatility on stage and screen was legendary.

At first glance his military career during the second world war was similarly versatile. According to some reports and obituaries in the days after his death, Lee served in the Special Air Service (SAS), Long Range Desert Group (LRDG) and Special Operations Executive (SOE). In reality he served in none. He was attached to the SAS and SOE as an RAF liaison officer at various times between 1943 and 1945, but he did not serve in them and never, as one paper stated, ‘moved behind enemy lines, destroying Luftwaffe aircraft and fields’.

When asked about his service record — which it should be pointed out was a fine one, with liaison officers performing a valuable link between the RAF and special forces — Lee didn’t exactly lie, but he did lead us on, encouraging us to believe it had involved more derring-do than it actually did. Asked about his wartime exploits in an interview in 2011 he said: ‘Let’s just say I was in special forces and leave it at that. People can read into that what they like.’

Pressed on the subject, he replied with melodrama worthy of a Hammer film: ‘We are forbidden — former, present, or future — to discuss any specific operations.’

Nonsense. Wartime members of those special forces units are not — and never have been — prevented from discussing operations. A decorated wartime SAS officer, Roy Farran, published an account of serving in the regiment as early as 1948.

When I wrote my own history of the SAS in the second world war, I did so with the full cooperation of the regiment, which put me in touch with more than 50 wartime veterans, all more than happy to talk.

Sir Christopher wasn’t the first by any means to buff up his war record. On the same day his death was announced I received an email from the SAS Regimental Association asking if I had any information on a soldier whose daughter claimed had served in the LRDG. I didn’t. Nor did the association. Between us we receive a couple of dozen such inquiries each year, from relatives seeking information about the wartime exploits of a grandfather/father/uncle.

They follow the same format. In their twilight years these ageing men revealed to their relatives that they had served in the SAS during the war. Blown up Nazi airfields in North Africa, derailed trains in Occupied France, that sort of thing.

And then the old men died, and their relatives understandably wanted to know more. The SAS Regimental Association is admirably restrained in how they deal with such inquiries, particularly given the audacity of some impostors. With only a handful of genuine wartime SAS veterans alive, the phoneys have fewer chances of being unmasked. They’ve done their homework, of course, read the books, watched the TV documentaries and polished their patter. One such man, now aged in his late nineties, has been attending association lunches for a number of years and as recently as this May was photographed at one such event.

This poses a problem for the association. When it’s middle-aged men they are quick to unpick the fabrication, as was the case in 2009 when 61-year-old Roger Day was photographed at a Remembrance Day parade wearing the distinctive sand-coloured SAS beret and 17 medals. Day’s undoing was to march in campaign medals stretching back to the second world war, and he was subsequently convicted of wearing ‘a decoration calculated to deceive’ and sentenced to 60 hours of community service.

But when it comes to challenging an old man in the last years of his life, the attitude of the SAS Regimental Association is ‘What’s the point?’ Allow them their fantasies because somewhere buried deep among the stories will normally be a burning sense of shame.

Why do men create such fantasies? Most did actually do their bit in the war; they are genuine members of the ‘Greatest Generation’, but at some point in their lives they decided their war record wasn’t quite great enough. So they embellish it, and what is more dashing than the Special Air Service with its ‘Who Dares Wins’ motto?

A few years ago I travelled across England to visit an old man who had served in the wartime SAS. Or so I’d been told by his family in a lengthy email. In fact he had been in North Africa in 1942 but in the RAF, a member of a maintenance crew whose valuable role it was to salvage crashed aircraft from the desert. At some point he probably encountered the SAS, and decades later he decided he’d been one of them. Yet while he could reel off places in Libya where the SAS had been active, he could name neither his squadron commander nor his sergeant. Not long into our conversation he knew that I knew he was making it all up (this was later confirmed by the regimental association) but nothing was actually said. He offered me some tea, we made small talk for a few minutes, and then I left.

Claiming to have fought in the wartime SAS is a relatively new phenomenon. Prior to 1980 it was the LRDG who were bothered by bullshitters. The 1958 film Sea of Sand, starring Dickie Attenborough, earned the unit worldwide recognition, as did a slew of books and a Hollywood TV series of the 1960s, Rat Patrol, loosely based on their wartime exploits in North Africa.

Men frequently claimed to have served with the LRDG, such as a Mr Falls, owner of a garden nursery in Leeds who, in an interview with the Sunday Times in October 1971, explained how his knowledge of exotic plants was acquired during his special forces service. As the unit’s newsletter explained in 1972, they had no record of Falls so they’d dropped him a friendly line. Be delighted to enrol you into the association if you would send details of your service record. No such details were sent.

It was the 1980 Iranian Embassy siege that changed things. The SAS, who so spectacularly ended the siege in South Kensington by abseiling down the building in front of the world’s television cameras, became the most famous regiment in the world and the target for men saddled with unfulfilled dreams.

Yet ironically this new found fame sat uncomfortably with many wartime members of the SAS, a band of modest men with no deep-seated insecurities. They didn’t spin yarns or shoot lines, and a good many told their families nothing of their wartime heroics. Lt Norman Poole, who died earlier this month aged 95, was an SAS officer who parachuted into Normandy ahead of the main D-Day invasion fleet. Credited with being the first Allied soldier to land in Normandy on 6 June 1944, Poole and the five soldiers with him simulated a large-scale airborne attack using 200 dummy paratroopers. What a tale he could have told but Poole never spoke about his days in the SAS. As his daughter said shortly after his death: 'My father was terribly private about all of this.'

Sir Christopher Lee had a ‘good war’, to use the vernacular of the time. But it would have been honourable of him to clarify exactly what it was he did. Unfortunately the actor in him couldn’t resist hamming it up. Does it matter? Yes, because his life was already rich in accomplishment and he’d acquired enough fame without having to win still more through the daring actions of others.

Most of these men did their bit. But at some point they decided their war records weren't dashing enough

Gavin Mortimer’s The Men Who Made the SAS: The History of the Long Range Desert Group was published last month.