Who Do You Think You Are? Daniel Radcliffe review: Nothing tugs at the heartstrings as devastatingly as real life

As the Harry Potter star makes a moving discovery about his ancestor, it is jolting to witness the chipper Radcliffe’s lightly worn bonhomie evaporate with one shake of a sorting hat

Radcliffe makes an emotional discovery about his great-grandfather (BBC)

It takes a good half hour but finally Daniel Radcliffe lives up to his side of the bargain on the returning Who Do You Think You Are? Clasping a letter that holds the tragic key to a long-lost family secret, the former boy wizard sniffles slightly and dissolve into tears.

There has, for much of the preceding 30 minutes, seemed a very real danger that BBC1’s pre-eminent celebrity blub-fest might skimp on the emotional devastation. But no, here it is – and with bells on. Radcliffe’s cheek-dampening moment (which admittedly falls short of full-on hanky blowing) arrives as he reads aloud the suicide note of his maternal great-grandfather to the wife he is about to leave behind.

The scene is obviously heart-rending. How jolting, in particular, to witness the chipper Radcliffe’s lightly worn bonhomie evaporate with one shake of a sorting hat. The missive also goes towards solving a decades old mystery: why did his mother’s side change their name from the more exotic Gershon to the stoutly anglicised Gresham?

Radcliffe’s hunch was that, this being the late Thirties, the family were eager to wallpaper over their Jewish heritage. The true motive, the archives reveal, was to allow the Gershon/Greshams move past the taboo of Samuel Gershon’s suicide at age 41.

He’d taken his life as the Hatton Garden jeweller’s business inherited from his father (a dead ringer for Radcliffe) teetered under crippling debt. These were desperate times for the husband and father of two. Samuel’s solution was desperate too. He and his brother apparently faked a robbery in order to cash in their insurance premium.

The police quickly rumbled the swizz. The pressure on poor Samuel was redoubled. One day he drove off and never returned. “You want to just reach into the past,” says Radcliffe. “[Say], ‘whatever you’re going through, you have so much to offer the people who are around you and they still would all have loved you’”.

Who Do You Think You Are?’s great achievement across the years has been to flesh out the humanity of its stars. We’ll never think of Danny Dyer in the same way after the series revealed his blood ties to right royal geezer Edward III. Ditto current affairs bulldog Jeremy Paxman, blubbing for England as he delved into his ancestors’s horrible histories.

The latest celebrity guinea pig is different in that Radcliffe has consistently come across as uncomplicated and humble – that rare child star not warped by early fame. It isn’t that he lacks a deeper side so much that he’s always presented himself honestly to the world. And so it continues here. With his gap-year beard and un-starry ways, he moves easily among the muggles on a journey that takes him from Southend to Banbridge (near Belfast).

Southend is where Samuel lived while commuting to Hatton Garden and the ultimately doomed jewellery business. The bleak conclusion to that story has its mirror in Ireland where Radcliffe catches up with the four great-great-uncles who marched off to the First World War.

Three made it back. But it’s the story of the fourth that captivates Radcliffe. Ernie had a sweetheart at home, whose love letters turned Radcliffe’s cheeks pinker than the Hogwarts rose garden. A happy ending of sorts materialises in the archives. Ernie and his beloved Jeannie married on Valentine’s Day 1915 and had a year together before he returned to the trenches where a stray German shell awaited.

Radcliffe’s lip wobbles precipitously as he takes it all in. There seems a fair chance he might break down once more. Reality TV and big budget drama may do their worst. But yet again Who Do You Think You Are? reminds us that, for muggle and wizard alike, nothing tugs at the heartstrings as devastatingly as real life, with all its triumphs, reversals and bittersweet stings.