by Nick Higham
BBC Art and Media correspondent
It wasn't the sort of birthday treat most 82-year-olds would relish, but the Duke of Edinburgh did his best to get into the spirit of the occasion.
He pointed out that the horses pulling the gold state coach were the wrong colour - they should have been grey not brown - and that the milk float was going into the wrong entrance.
The management at the Legoland theme park near Windsor promised to make the necessary changes.
The Windsors are taking part in British Tourism Day
Some of the 2,000 local schoolchildren, specially invited for the day, sang happy birthday, but a Legoland suggestion that the Duke might like one of the special badges given to ordinary birthday visitors was discreetly vetoed by Palace officials.
As for the Queen, she listened impassively as Lego's chief executive, Kjeld Kirk Kristiansen, grandson of the company's founder, showed her the park's miniature version of her London home.
35 million bricks
She remained composed when shown the band of Lego guardsmen trooping the colour on a Lego horse guards' parade, watched by a tiny Lego Queen sporting a yellow coat that almost matched the outfit worn by the real thing.
The only time she showed any animation was when she spotted a Lego model of the former Royal yacht Britannia, moored in a miniature pool of London next to Lego versions of Tower Bridge, the Tower of London and the London Eye.
Miniland, as its called, is the centrepiece of Britain's Legoland, one of four Lego theme parks around the world - a demonstration of just what you can do with 35 million children's building bricks and unlimited patience.
Visitor numbers at Legoland are down by 100,000 from last year
The Queen and Prince Phillip - themselves two of Britain's biggest tourist attractions, in a manner of speaking - were there as part of a Royal day devoted to tourism.
From the entrance to the park they were able to admire the spectacular view of Windsor Castle a mile or two away - surprisingly less popular as a tourist attraction than Legoland.
The castle got just over 900,000 visitors last year, Legoland 1.5 million.
They could also admire the planes taking off from Heathrow carrying some of the 24 million foreign visitors who come to Britain each year, spending £12bn between them.
Global tourism has taken a knock in recent years, what with the aftermath of 11 September, the Iraq war and now Sars.
The numbers visiting Britain in April fell by 15% compared with the same month the previous year, and Britain's tourist attractions also suffered from a foot-and-mouth outbreak in 2001.
Prince to Edinburgh
No fewer than nine Royals fanned out across Britain to bang the drum for the industry.
The Prince of Wales was in Edinburgh, visiting historic attractions along the Royal mile.
The Duke of York was in the Lake District.
The Earl of Wessex was in Wales, where 10% of the economy depends on tourism.
And his wife was in the West Country, where tourism is even more vital, visiting the open-air theatre at Minack in Cornwall and a family farm near Ashburton in Devon.
VisitBritain, the old British Tourist Authority, has plans to reinvigorate the industry.
The Queen made a whistle-stop tour of her (miniature) kingdom
American tourists especially have stayed away in the wake of September 11th and the war in Iraq.
VisitBritain is repeating last year's US television ad featuring the Prime Minister, Tony Blair, who was apparently "the most influential ambassador for Britain with US audiences".
The organisation is targeting new markets, like China, Russia and Poland.
And its urging British tour companies, hotels and visitor attractions to adapt to a changing world in which short breaks, business travel to conferences and exhibitions, and do-it-yourself holidays booked on the internet are all growing in importance.
Back at Legoland, the numbers are holding up well this year despite the global difficulties - perhaps because most of its visitors come from the UK rather than abroad.
Nonetheless, visitor numbers at the park last year fell 100,000 from 1.6 million the year before and it has yet to show a profit after seven years of operation.
Not surprisingly the park's managing director, Mads Ryder, was pleased by the Royal visit and the publicity he hopes it will generate.
But next time they arrange a Royal visit you couldn't help thinking they'd do better to invite some rather younger members of the Royal Family.