GRAND Designs is the Channel 4 housebuilding show where the budget is always over, the deadline is history, and at least one of the prospective tenants is threatening divorce if they have to spend another month in that rotten caravan.

The similarly titled A Royal Grand Design was entirely different. It is that word “royal”. It changes everything, as we saw in this documentary, ten years in the making, about the rebirth of Dumfries House in Ayrshire under the keen eye of King Charles, or the Prince of Wales as he then was.

There was no caravan on site for Charles, but he did confess to the odd sleepless night over the £45 million purchase price. It had been an “appalling risk” for the consortium he led to take out such a large loan, he told the filmmakers.

But just look how handsomely it has paid off. Over the course of the next hour the viewer was invited to marvel at the changes Charles had brought about. He saved a collection of Chippendale furniture from being broken up and scattered abroad.

He rebuilt the walled garden, added a cook school, an adventure hub, a teaching farm, architecture centre, and so much more.

He set up apprenticeships in ancient crafts and created good jobs in a former mining area where there were precious few.

“I wanted to try and make a difference to the local area,” said Charles. “It had many of the worst indices of unemployment, ill-health and everything else. I’m one of those people who rather likes taking on the difficult challenges.”

All very impressive, and it would not have been any less so had the programme been more probing. We were constantly encouraged to look at Dumfries House and its grounds as unquestionably a good thing. More than this, it was presented as a prototype, a sort of “Charles’ World” theme park (though no-one would have dared call it such) that could be reproduced elsewhere.

Where the money would come from was one of several details that were missing. I would have liked to have known more about the consortium he put together.

We were told 300 people were employed at Dumfries House, but not the exact number of locals on the payroll. And might the local area be better off with a new manufacturing plant rather than another stately house for folk to wander around?

But this was not that kind of documentary. This, said narrator Richard E Grant, was a film that provided “an insight into the real man behind the crown”.

Charles was in a splendid mood throughout, no pen-related drama in sight. The various restoration experts were good value, particularly Charlotte Rostek, the curator, who tried out the Chippendale bed. “It’s definitely a shoes off, white gloves moment,” she said, making herself comfy.

We met James Hardie, the Chippendale restorer, at work, and another expert repairing the fabric of a chair that was most definitely not for sitting on. It was like a very grand episode of The Repair Shop (on which Charles appeared recently).

The locals interviewed had good things to say about their royal neighbour and employer. One dogwalker remembered having a chat with Charles. Five months later he bumped into him again and was amazed to find he remembered the dog’s name. Another interviewee, a young butler, was thriving in his new job. “I’m driving, living on my own, know how to work the washing machine.”

Good for him, and for Charles for making his vision a reality. But really, Sir, as everyone called him, the odd sceptical note would not have sent the house tumbling down.

Read more: Your verdict on new BBC1 show The Traitors?