SAS hero Chris Ryan, pictured, was the only one of an eight-man squad to escape during the Bravo Two Zero mission of the first Gulf War in 1991.

He earned his place in the history books with the longest escape and evasion by any soldier, covering 190 miles in getting to the Syrian border.

The mission caught the imagination of many people and prompted several books based on what happened to the team of soldiers; it was this that started Ryan on his second career as an author.

“I was approached by two writers who wanted to do an adaptation of my story,” he explains. “And I agreed but, rather naively, I didn’t have any consultation rights and I wasn’t totally happy with the result, so I thought I would approach a publishing house to see if they would publish my account.”

The result was Ryan’s first book The One That Got Away, which was a bestseller, and he hasn’t looked back since, with a whole host of both novels and nonfiction works under his belt.

The latest novel is Osama, which offers the author’s trademark informed fiction.

It explores the idea that Osama Bin Laden was not killed by American forces but was already dead when they entered his compound.

“It seemed to me like a good basis for a conspiracy theory,” says Ryan. “It is fiction but it is as realistic as possible.”

Ryan retired from the army after the Bravo Two Zero mission and now lives in the USA, but he will be in Salisbury signing copies of Osama at Waterstones on Friday at 1pm.