When Kevin McKidd wishes to remind himself of the bluntly violent experiences that inform the behaviour of his latest character, he retreats to his trailer. From a pile of books, he chooses one of several diary-style autobiographies written by army trauma surgeons and falls back into the horror of treating grievously injured colleagues and friends in the midst of a battle zone. “You have to keep reminding yourself how bad it is for them,” he says, “and how proud they are of the men they manage to save.”

For McKidd’s latest role, he joins the cast of Grey’s Anatomy, the hugely successful American medical drama set in a Seattle hospital and now in its fifth season. He plays Owen Hunt, a military surgeon who was recently discharged from service in Iraq and carries a brooding sense of disquiet stemming from his battlefield experiences. In his first scene, he treats a patient outside the hospital by performing a tracheotomy using a ballpoint pen, a procedure that is jarringly brutal.

“The hospital staff are shocked, because it’s not sterile, it’s not protocol, and I say, ‘Well, I cleaned the pen with a handful of snow.’ The guy’s still alive, but because the pen is inserted with such force, it damages his windpipe and he suffers complications. These surgeons are coming back to civilian medicine and learning they don’t have to be so balls-to-the-wall, but it’s all this guy has known for four or five years.”

McKidd possesses a convincing capacity to provide both surface and depth. In researching his role, he spoke to a former army surgeon by conference call, collected a series of autobiographies and studied the acclaimed documentary Baghdad ER, detailing the work of surgeons away from the front line. With troops still serving in Afghanistan and Iraq, he feels a sense of responsibility to colour his performance with a vividness taken from stark reality.

Later in the series, his character relates a story from the battlefield of treating a fallen soldier. The victim was losing blood from so many wounds that Hunt instinctively hurled himself on top of the patient, to use his own body weight to stem the flow. It was a scene based on a real event. Battlefield surgeons work outside the realms of medical convention. In his conference call with the former army surgeon, McKidd was struck by his brusqueness.

“They’re the type who don’t suffer fools gladly, and I asked layman’s questions which he found hard to digest because they are so beyond the knowledge base that we’re on,” McKidd says. “He put up with me. They had to be very quick-thinking out there — the textbooks don’t apply when you’re on the battlefield. It’s only in the last couple of decades that medicine has gone to the front line.

“It used to be that many soldiers died on the way back to Mobile Army Surgical Hospitals. So there’s a pride in these guys for the techniques they’ve developed to bring triage surgery right there. They’re pushing the boundaries out of necessity.”

Hunt’s brusque manner unsettles fellow male surgeons, although he becomes a love interest for one of the long-standing female characters, Dr Cristina Yang — a typical plot line for a show in which one male character is dubbed McDreamy and another McSteamy. Grey’s Anatomy is a gentle but keen observation of the tangled professional and personal lives of a group of wry, beautiful people. It lacks the gritty authenticity of ER, but is more polished and affirming than any UK medical drama.

The arrival of McKidd’s character brings a sense of darkness, an unsettling anxiety. In preparing for the role, he also sought the advice of an army liaison expert who works with veterans suffering from post-traumatic stress disorder. The tremors of the battlefield still agitate just below the surface of Hunt’s personality.

“Because this character represents these people, I thought I should do some thorough research,” he says. “I don’t want to get too lofty about it, because it’s a TV show and it’s entertainment, but it’s brave to put a character who’s suffering from post-traumatic trauma and is talking about a war that is still ongoing in a prime-time show. A lot of people suffer from post-traumatic stress and because of their pride, many suffer in silence. One of the biggest problems is getting people to open up and that’s what TV can do sometimes. I’ve had letters from people whose loved ones suffer from it and they’ve been complimentary.”

The commitment to his craft and the diffidence with which he seeks to undermine its potential for pomposity are accurate reflections of McKidd’s nature. He has spoken in the past of joining the Moray Youth Theatre group while growing up in Elgin because he was too fat to play football, and he once revealed that his mother sent him a diet plan from the Richard and Judy show. There is a cheerful lack of pretension to McKidd, a guileless maturity that grants him immunity from the sort of billowing ego that often inhabits his profession.

There is a sense, in considering his acting career, of fame being inclined to keep a watchful but aloof eye on his progress. He notoriously missed the photo-shoot for the iconic Trainspotting movie poster, to go on holiday with his girlfriend to Tunisia, and while fellow cast members such as Ewan McGregor and Robert Carlyle were bestowed with an immediate celebrity, McKidd subsequently worked as a barman and a bicycle courier to make ends meet. He even walked home in the rain from the film’s premiere because he did not have the cab fare in his pocket.

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