The Prime Minister jumped out of his Jaguar and headed for the Old Govan Arms on Glasgow’s South Side. The plan was to pop into the pub where his father used to drink before the war, when the family lived round the corner. But when prime ministers go for a drink these days, they do not do so unaccompanied.

A small army of reporters, photographers, security officials and Downing Street advisers shouldered their way in after him and encountered the city’s renowned sense of humour. “What is going on?” demanded a man at the bar. “Have Rangers signed a new player or something?” Tony Blair explained that he was there to revisit his dad’s old haunts. “Have you come to pay off his arrears, then?” asked another drinker.

Grinning broadly, Mr Blair set off down Golspie Street to walk past the place where his father’s house — long since demolished — had once stood. Earlier he had stood on a makeshift platform in the echoing surrounds of the Govan shipyard and explained: “My dad was brought up in Govan in the Twenties and Thirties. He was a foster child and his foster father was a casual labourer in the yard. It’s interesting to see how much has changed."

As he loitered on Golspie Street, in search of the exact spot where the house had been, a car drew up and a window was wound down. “Can I get my photo took with the Prime Minister?” asked a young woman. “Why not?” said Mr Blair. Anne Marie Clark climbed out, draped her arms around the Prime Minister on the left and the First Minister of Scotland on her right, smiled winningly at a phalanx of photographers in true celebrity style, then nipped back to the car. “Are you a Labour supporter?” asked a reporter. “Well I am now,” she shot back. “Who wouldn’t be?”

There is a widely held view that the Scottish National Party’s lead in the polls owes much to the Prime Minister’s unpopularity north of the Border. That may be the national view, but in Labour’s heartland, where the votes have to be shored up on May 3 if the party is to stand a chance of closing the gap with the SNP in the Scottish elections, he is still a formidable campaigner.

The message delivered in the cavernous hangars of the BAE Systems shipyards at Govan, where the latest Type 45 Destroyer is being built and where more than 4,000 jobs depend on future orders, was unmistakable: vote SNP and all this could be put at risk. “Who is going to place an order here if there is an independent Scotland?” asked Ross Frew, 22, one of 350 apprentices taken on over the past four years. “Other countries will want to see the work going to their own people, not to us.”

BAE Systems had helpfully supplied an attractive young woman sheet metal worker to go round the plant with the Prime Minister and explain some of the finer points of the latest innovation — a plasma steel cutter. Sheryl Dobie, 21, who has just completed her apprenticeship, was impressed as much by Mr Blair’s charm as by his views on cutting edge research. “He’s quite the thing,” she pronounced.

Her view, and that of most of the workers assembled to hear the Blair message, was that voting SNP was a high risk option. But it is an option that most Scots seem to find attractive. Mr Blair summed up the argument succinctly enough himself in the course of an earlier speech in Glasgow: “The SNP say to Scotland, ‘Go on, we’re doing well, there’s nothing to fear; why not?’ . . . To which the answer is a better question: why? What is the reason for doing it?”

It is a good intellectual debating point. Whether Scotland is prepared to listen to it is another matter. Once an electoral drift has begun it is mighty hard to reverse and with only three weeks to go there is little sign that Labour is succeeding.

Contrary to the idea that he has never warmed to Scotland or the Scots, Mr Blair assured us that he felt close to it. “Scotland’s really in my blood, in the sense that I was born here — but it was also a huge part of my childhood.”

It may also have to become a huge part of Mr Blair’s final weeks in office if he is not to go down in history as the Labour Prime Minister who lost Scotland.

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