It was only after his grandfather died that Humphrey Ker, one-third of sketch team The Penny Dreadfuls, found out about his amazing war record.

“We knew he was a senior officer in the Royal Navy during the Second World War,” says Ker of his mother’s father Dymock Watson.

“But his obituary said he had been seconded into the Special Operations Executive, a little-known elite force which was dumped into enemy-held territory to help local resistance fighters.”

Ker’s research into his grandfather’s wartime deeds have formed the basis of his one-man show Dymock Watson: Nazi Smasher!, as he recounts a dangerous mission to sabotage an Axis oil pipeline in Romania.

“Under the Official Secrets Act his file is classified until 2031,” says Ker.

“I have put in a request to have it declassified, but I’ve not had any response back. I grew up in a military family, reading Commando comics, so I wanted to do a show about it, with a comic side to it.”

Ker plays his ancestor and a cast of characters, using what he knows for certain about his grandfather’s Romanian mission as the basis.

“At one point I had him going to Berlin to assassinate Hitler,” he says.

“But I think there’s enough in the story already, and I didn’t want to be disrespectful either.”

Ker admits his military obsessions have been kept reined in by fellow Penny Dreadful cast members Thom Tuck and David Reed over the past nine years.

His dream of joining the Army himself was scuppered by his lofty height – having realised that it would most probably make him an easy target.

“If you’re going to pick who to shoot from a group of ten people, you’re going to go for the one who’s harder to miss,” he says, recounting a tale of a 6ft 6in-tall Army friend of his father’s who spotted freshly painted graffiti offering “£100 to whoever gets the big b******” on only his second patrol of Belfast’s notorious Falls Road.

“The thing I’ve been most excited about has been going to a re-enactor’s website and buying a 1941 British paratrooper’s uniform to wear in the show.

“This is allowing me to play out my fantasies of running around and shouting a lot without being shot at.”

His solo show, which is still a work in progress, is his first away from the group, which has decided to go on hiatus for this year’s Edinburgh Fringe.

“The Penny Dreadfuls’ solo shows are reflecting our personalities,” he says.

“Dave is doing something quite cool, Thom’s is about Disney DVDs so he can talk about The Little Princess, and I’m talking about the spring mechanism on a Mark II Sten gun.”

The Penny Dreadfuls are best known for their three Victorian-set Aeneas Faversham sketch shows, which Ker hopes may be brought to television audiences soon.

“With our Victorian shows we always said the audience shouldn’t need to have any knowledge of the period,” he says.

“We didn’t want it to be something only academics could come to and stroke their chins to satire about the repeal of the Corn Laws.

“It was about creating our own world, in the same way The League Of Gentlemen and The Mighty Boosh do. You can talk about an awful lot with historical comedy, it shines a different light on the way people behave.

“What I love about British history is that absurd, over-the-top way British people used to be – in the Victorian period they were at the forefront of science and industry, but when someone produced a photograph of fairies they believed it.

“The World Wars ground that out of people, they saw how harsh the world was. They didn’t have that child-like enthusiasm, which is such a gift for comedy.

“I like celebrating funny things rather than being negative – I don’t like to laugh at people, I like to laugh with them.”

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