IT’S easy to be cynical about royal documentaries. In fact to call some of them “documentaries” can be a stretch in itself. This one, about Prince William ’s heartfelt homelessness campaign, falls midway between Phillip Schofield ’s risible film about Prince Philip's carriage driving, and Ant & Dec’s cheeky efforts with the then Prince Charles about the Prince's Trust.

On those occasions everyone was having a hoot. The tone is far more serious here, as it should be, although Prince William himself is confident and relaxed in his views on the subject as he's interviewed by a Bafta-winning director on a comfortable sofa. No reason why he wouldn't be.

He’s appears to be on top of his brief. William explains in some detail over an old picture of himself, his estranged brother Prince Harry and their mother Diana, how they went to The Passage, a homeless shelter when they were still in short trousers. What an odd place to take your children, you might say.

Of course, she was preparing the boys for a life of charitable service. It paid off, mostly – although Harry very much ploughs his own farrow. William later reveals how he talks to his own children about homelessness while they're on the school run.

Are they getting too old for Harry Potter audio books? Nonetheless, if you wanted the next episode in the Royal soap opera in this film, you’ll be disappointed. The picture of Harry passes without comment, as we’re dealing with an issue the Prince William genuinely.