Charles Dance delivers a warm, tender and revelatory Who Do You Think You Are?

But Dance is, as he put it in tonight’s fascinating Who Do You Thing You Are?, not posh at all. His origins (as he also intimated in this Radio Times profile) are fairly humble and he is anything but stern and snooty. In fact, tonight we saw a lovely, sensitive man making some stunning and intriguing discoveries about his family.

Before he made the programme Dance knew very little about his father Walter Dance (below) who died when he was four. In fact he only had one picture of him.

It seems extraordinary that at the age of 70 Charles had never made serious enquiries – a reason which was perhaps never satisfactorily explained or explored in tonight’s show (my only real gripe with it).

But his discovery was fascinating – starting with the realisation that his Dad was actually 72-year-old when Charles was born – 26 years older than Charles had believed all his life.

'It's rather extraordinary to know that here in my 70th year, I am only finding out about all of this now," he said, with some degree of understatement. But it spoke of a wider truth – about how family stories become truth, how myths are believed and are passed into fact for reasons which will usually remain a mystery.

His father’s missing years (as far as his actor son was concerned) were devoted to a whole different life – and another family.

Unbeknownst to his actor son, WD - as Charles always called him - served with the Royal Fusiliers in the Boer War in 1900 when the conflict entered its most brutal guerrilla phase; WD was forced to engage with a daily hunt for saboteurs which was physically and mentally draining.

Winning a campaign medal, WD returned to England and then went back to South Africa with his wife Louie later in life. Louie, the woman WD married before he married Charles’ mother Eleanor, had two children with him almost 50 years before Charles was born.

The first, Norah, and a half-sister Charles never knew about, was born in December 1898, in the C19th.

“I have a sister, I see, right,” Dance said, clearly overcome with emotion, telling the historian who helped him uncover the truth: “I have to say this is quite moving, because I know so little. So gradually, bit by bit, we are finding out about the life of a man who I just knew by his name, WD. You have been able to tell me an enormous amount, thank you.”

He was then told of another half-sister, Mary, born in 1903. She died at the age of five in unbearably tragic circumstances - a grisly accident when she was hit on the head by a scaffolding pole and was rushed home where she died.

Added to that, Charles discovered that WD wasn’t divorced from his first wife when he married his own mother Eleanor.

What was striking about the film was Dance’s sincerity. Sometimes this show can attract the waterworks in a manner which can, occasionally feel a little contrived. Not so here. And the moving nature of the discoveries didn't need any embellishments.

“It is overwhelmingly sad and I don’t think, as a parent, that one would ever get over something like that,” Charles said of the death of Mary.

We also learned that Norah died in 1993 but the story didn’t end there, with Dance visiting her granddaughter Noneen in Pretoria, where he was shown new photographs of his father and, for the first time, Norah herself.

He also discovered Norah had written an unpublished memoir that painted a vivid picture of WD and he also met his other surviving relatives in some beautiful scenes.

One line in Norah’s memoir tickled Dance quite a lot: "He was a loveable and a generous man and was slow to anger... and liked to be considered a ladies' man.”

His son said with some admirable candour: “I think that is a quality, not a fault. I think I have inherited quite a lot of that, really.”

Fighting back tears as he looked through the book, we witnessed the actor as if he were meeting his father again.

“I don't know why this is quite so overwhelming, but it is,” he says.

It’s a pretty impressive start to the series which will air four more films in the coming weeks with a further five in the autumn.

The first tranche will see Craig Revel Horwood, Clare Balding, Adil Ray and Emma Willis investigate their family past. In the autumn Lulu, Fearne Cotton, Ruby Wax, Noel Clarke and Lisa Hammond will comprise the second chunk of series 14.

Can they be as revealing?

Executive producer Colette Flight tells RadioTimes.com that they will provide some more stunning disclosures.

Fearne Cotton discovers that her great grandfather was a conscientious objector while Adil Ray traces his own links to Ugandan Royalty.

Clare Balding will find plausible evidence that her politician great grandfather Sir Malcolm Bullock was homosexual.

“She had always heard rumours in the family that he was gay and she wanted to get to the bottom of it,” says Flight.

“Homosexuality was illegal and it’s not easy to research because of that and her conclusion is that he probably was.”

Presenter Emma Willis is perhaps the most revealing film, she adds. She has to swallow what Flight calls some “disturbing” truths about an C18th ancestor of her who was involved in interrogating Catholics during the Irish Rebellion.

“it’s quite difficult history,” says Flight. “It’s a turbulent time in Irish history and it’s quite graphic, some of the things she discovers. Her ancestor was a loyalist. He was involved in a...disturbing incident I would describe it as, around the time of the Irish rebellion. He was involved in interrogating Catholics. The descriptions of it is disturbing and it’s hard to read that kind of thing.

"She handles it with real grace and sometimes what you discover in your family history isn’t necessarily what you want to find but she handles it very well.”

Rather like Charles Dance.

Who Do You Think You Are? continues on Thursday nights on BBC1