James Blunt, the singer who suddenly bestrides the pop charts, is an unlikely modern superstar. Schooled at Harrow, the 28-year-old troubadour is a former army captain who served in Kosovo, guarded the Queen and took part in the Queen Mother’s lying-in-state. His cut-glass accent is a tribute to the Household Cavalry.

At the beginning of the year Blunt was a virtual unknown. Last week he achieved a double whammy when his single, You’re Beautiful, and his debut album, Back to Bedlam, claimed the number one spots. Both are remarkable, having risen by word of mouth rather than the more usual route of crashing in on a wave of hype.

Of course, Blunt is not the first pop star to have done time in the armed forces. Elvis Presley served as an army GI in Germany, Jimi Hendrix was a paratrooper in the 101st Airborne Division and the reggae artist Shaggy drove a tank during the first Gulf war. But they were not officer class.

Blunt’s publicists were at first inclined to play down his pukka Sandhurst background — as is the singer himself, whose tousled hair, unshaven face and motorcycle leathers are a defiant reproach to the plumed helmet and shiny leather boots that he once wore. But his warrior status, burnished by his account of how he went into combat zones with his guitar bolted to the outside of his tank, has proved the key factor in his appeal.

It helps that he possesses what one writer described as the voice of a fallen angel and writes clear and emotional lyrics. He is also devilishly handsome and his concerts are packed with women, aged from 16 to 30, accompanied by reluctant boyfriends. Blunt has a slightly different take on his audience profile: “People say a lot of good-looking girls are turning up at my gigs but that’s why a lot of men come. They come along to a James Blunt show so they can meet pretty girls. ”

The music scene is awash with talented singer-songwriters who find it hard to break through. Manufactured pop groups may be on the wane, but prepackaged records are more easily sold than songs with character that take time to catch on. What marks out Blunt is that the death and suffering he has witnessed are reflected in his heart-rending songs.

He wrote one of his numbers, No Bravery, in Kosovo while lying in his tank inside a sleeping bag with his boots on. Its moving lyric runs, “Brothers lie in shallow graves / Fathers lost without a trace”. He recalled: “You’d walk into burnt-out houses and fields with mass graves and feel a sense that someone or something incredibly evil had been there.”

Love songs also loom large in his repertoire. He recorded Goodbye My Lover in the Los Angeles home of the actress Carrie Fisher, to whom he had been introduced by a friend. “Carrie said, ‘If you’re doing an album, you might as well come and live in a weird house’. So she was my landlady and I recorded in her bathroom because she keeps a piano there, which is the kind of thing they do in Hollywood.”

At the heart of his songs, he says, is “the lonely path one walks through life, the connections you make and the thoughts that you don’t generally share with people. I’m a loner, but I’m comfortable with that”. Many of the lyrics feature his love affairs with former girlfriends, of whom there appear to be many, although with more discretion than those of most pop singers they have not yet surfaced in the gossip columns. Paradoxically, he says: “I am not very emotional, as any ex-girlfriend would tell you.”

The image of poet-soldier fits well with his family’s military history which stretches back 1,000 years to the time when his ancestor King Gorm of Old Denmark (“That’s where the term gormless comes from”) sent his son to England in the 10th century. The family’s fair hair earned them the surname Blond, which transmuted into Blount. The singer shortened it to Blunt, which he thought more catchy, when he left the army in 2002 after five years’ service, intent on a musical career.

Blunt felt that he was earmarked for the army from the moment he was born at Tidworth military hospital in Hampshire in 1977. Both his grandfathers and all his uncles had served their country. His father, a cavalry officer in the 13th/18th Hussars, later transferred to to the Army Air Corps to fly helicopters and recently retired with the rank of colonel. His mother works in the travel industry.

It was not a musical family. “My dad was really practical and saw music as just a noise,” he said. The family’s only CD player was in the car, stocked with just three CDs — American Pie and two albums by the Beach Boys. He made unrewarding attempts at playing the violin at the age of five and later tried to learn the piano: “I really hated it. I remember thinking this is the most miserable thing.”

His musical awakening occurred at Harrow when he saw an older boy, Henry O’Bree, playing an electric guitar: “I was hooked. I saved up and bought myself a £100 guitar.” He announced to friends his ambition of becoming a musician and formed a band. “It was truly dreadful,” he admitted. The audience threw food.