For Germans, it was a vision of the future. Debonair in his sleek dark suit, the suave politician gave a regal wave to the crowd, sharing a secret smile with Chancellor Angela Merkel, standing at his side. She looked on, adoring, her dour features quite transformed as the crowd roared their approval for the man beside her. Suddenly, the fraulein’s saturnine features rearranged themselves into an uncharacteristic broad grin. He merely adjusted his lilac tie and permitted himself a quiet smile. Later, he delivered a paean to the leader, saluting her success in steering Germany through stormy economic waters, saying: “Dear Angela Merkel, we thank you and stand as one behind you”.

Just who is this sophisticated European statesman? Meet David McAllister. He was last week mooted as Merkel’s heir apparent at Germany’s ruling conservative Christian Democratic Union party conference in Hanover. Bizarrely, however, his supporters at the congress waved banners proclaiming “I’m a Mac!” — for this leader-in-waiting is a not-so-secret Scot. The son of a wartime British Army captain, McAllister is the first dual German-British citizen to hold prominent public office.

Until last week, he stood out in Germany’s political scene mainly for his strange name, which the Germans struggle to pronounce. Last week, his reputation vaulted far beyond his unusual heritage. With the nation watching, McAllister, 41, played host to Merkel and the Christian Democratic Union as the party gathered at his northern Germany power base in Lower Saxony. It was a triumph for both politicians. Merkel was re-elected party leader, while McAllister was effectively anointed as her political son and likely successor. If Germans were in any doubt that a man who married in a kilt, supports both Hanover FC and Glasgow Rangers and still has a taste for Irn-Bru could one day be their leader, they were dispelled amid the near giddy scenes that greeted his and Merkel’s combined appearances.

McAllister’s rise has been meteoric. Climbing quickly through the party ranks, in 2010 he became the prime minister of Lower Saxony — despite the fact that Germans have such trouble pronouncing his name that he is often referred to as “Mac” by headline writers. “Every German has been to McDonald’s countless times,” McAllister has said. “But they somehow can’t seem to get it that an A follows the C in my name.” McAllister is not keen on Scottish stereotypes, but he has cannily turned this difficulty with his name to his advantage, creating the slogan “I’m a Mac”, as he campaigns for re-election as minister-president next month. Indeed, far from downplaying his Scottish roots, McAllister reminded the Hanover audience that Sir Gordon Macready, who administered Lower Saxony after the war, was the last leader of the state to run a surplus, which McAllister has committed to do. “Was he Welsh? No!,” he asked, rhetorically. “Was he English? No! Was he Irish? No! He was from Scotland!”

The crowd loved it. Marcus Kerber, head of the Federation of German Industries, who was at the event, says: “I would have thought that boasting about his heritage would backfire, but it didn’t. I think the Scottish notions of hard work and of fiscal prudence fit well with the mentality in northern Germany and there is a latent anglophilia in Lower Saxony that works for him. If you took away the Channel it would join up easily with East Anglia. There is a great deal of cultural affinity.”

Indeed, the more ardent among McAllister’s supporters have sported tartan scarves and ribbons at his rallies. So just how Scottish is McAllister? His father, James Buchanan McAllister, was born in Glasgow in 1919. He fought for Germany’s liberation in the 51st Highland Division and later returned with the Royal Signals Corps to West Berlin, where he met and married Mechthild. A German music teacher, she was asked to give voice lessons to British soldiers, to improve their speaking skills. They fell in love, but at the time marriage between Britons and Germans was frowned upon. The pair had a daughter out of wedlock in 1960, and went on to marry in 1964, as anti-German sentiment dispelled. They had another daughter, while David James McAllister was born in 1971. Young David was brought up in a small British colony in divided Cold War Berlin. He was raised bilingually, and went to a British primary school.

“I felt British”, he recalls. “It was a very British upbringing. British network, British schools. While most of the other children went home to relatives in Britain, I had a German mum, so I grew up fluent in both languages. The small, semi-detached houses were a piece of England in the middle of Berlin. On the streets, English was spoken. The smaller roads were named after British writers, Bronte Way, Shaw Lane, Dickens Way. Playing outside, we automatically learned English literary history. We read Charles Dickens at school.”

Photographs show him dressed in his school uniform of white shirt, yellow and black tie, grey pullover and short trousers — the image of a British schoolboy. He remembers waiting for his father to return from military headquarters, bringing an English newspaper. “He would bring home the Daily Telegraph from the office and we would read it together as early as 1977, when the Rhodesian war was the big news,” he says. With his father, he listened to James Alexander Gordon read the football results on the British Forces Broadcasting Service. He recalls early confusion about his identity.

Reading Victor magazine’s war stories, he questioned why the Germans were always the baddies. The family’s social life centred on the Country Club in Berlin, where they played tennis, swam in the pool or gathered for a traditional Sunday lunch. When his father retired in the late ‘70s, the McAllisters had to decide whether to return to Britain, or stay in Germany. They chose to remain, moving in 1982 to the lakeside town of Bad Bederkesa in Lower Saxony. He says: “It was more or less clear to me that we had turned German then.”

A lawyer by profession, McAllister is manifestly proud of his Scottish roots, eating shortbread at Christmas and taking milk in his tea — unusual on the continent. He is still in contact with cousins living in Newton Mearns and Edinburgh. He told the Telegraph, with just the faintest trace of a German intonation: “Of course if you have a surname like McAllister, you are always asked obvious questions: Do you play the bagpipes, are Scots mean ... and so on.” He cultivates British political ties, attending the Conservative Party conference and meeting David Cameron as recently as October. For all his affinity with things British, McAllister long ago made it clear that he opted for the land of his birth, not his father. Though he may have proposed on the banks of Loch Ness and married in a kilt, it was one of only two public occasions he has worn the garment. The other was the wedding of a Scottish cousin. He may retain the British passport — against his party’s guidelines — but says he has not used it “for 10 or 15 years”.

In the past, he said he was “more or less completely German. I’ve lived in Germany all my life. I did all my school in Germany and my military service in Germany.” Perhaps nothing marks McAllister out as truly German more than his attitude to the European Union. “We in Germany think that more Europe will be the solution,” he told the Telegraph. “That’s the difference between German politicians and British politicians. They say less Europe, we say we need more collaboration when it comes to the labour market, economics and finances.”

He still lives in Bad Bederkesa with his wife Dunja, and two daughters, Jamie Elizabeth and Mia. Not everyone is convinced that “Mac” is one of them. McAllister has admitted to receiving the occasional nasty letter or email “from elderly men of the very far Right”. By and large, however, the electorate seems to have been reassured by the fact that he sounds resolutely German and has lapped up his Scottish quirks. For now, it seems the only way for Mac is up.

— The Telegraph Group Limited, London, 2012