Last Night's Viewing: Who Do You Think You Are?, BBC1 Jet! When Britain Ruled the Skies, BBC4

You do sometimes wonder about the posthumous contributors to Who Do You Think You Are?, those sepia figures, so stiffly putting their best face forward, who peer out of dog-eared family photographs as their character and deeds are described on air.

They're almost always past caring, of course, but what would they have thought if they could have known that one day their peccadilloes and secret sorrows would have been the stuff of primetime entertainment? What would Gladys Barraclough have felt, more pertinently, to know that her appearance in a Yorkshire court to make a Bastardy Application against Alfred Stewart, would one day be shared with millions by her son Patrick Stewart? Might it be fair to suggest that pride at her son's celebrity would be mixed with a certain degree of social dismay?

Gladys won, incidentally, successfully forcing Alfred to acknowledge paternity of their first son, Jeffrey, and, very belatedly, to make an honest woman of her eight years later, when he returned from his first stint in the Army. That deprived Stewart of the possible explanation he'd been seeking for the fraught relationship between his father and his older brother. But it did suggest that Gladys wasn't quite as meek as his first memories of her had suggested – or her patient endurance of her husband's domestic violence. And it was that scarring element of Stewart's childhood that had focused this episode of the genealogy series – unusually – on a single predecessor. He didn't want to delve back six or seven generations. He just wanted to go back one and work out what had made his father so painful to live with. It was a Bastardy Application of a kind.

It was a moving one, too, as Stewart built on the war stories his father had told him as a boy to get a larger picture of what the war had done to him. He visited France, where his father had been sent with the BEF in a rear-lines battalion that was expected to lay train tracks rather than fight. But when the German offensive crashed through the Ardennes, these barely trained men found themselves facing Panzer divisions and Stuka bombers. The Imperial War Museum – that matchless repository of humble agonies – offered up a diary by one of Alfred Stewart's fellow soldiers, filling out some of the details of the horrors he witnessed. And back in Yorkshire someone had found a cutting that referred both to Stewart's battlefield promotion and the fact that he was suffering from shell shock.

That round dropped right on target, the actor stopping at the words as he read them out, his father suddenly reconfigured as victim rather than villain. And although Stewart Senior later volunteered for the Paras, dropping into southern France towards the end of the war, it was less the evidence of his military courage that mattered to his son than the evidence of his vulnerability. Talking to a campaigner for traumatised soldiers, Stewart realised that his father's violent anger possibly had its origins in fears and stresses that could find no other outlet: "Right at the heart of that history is a human being," he said, "and I don't think he'd been a human being for me before."

As a former member of the BOAC Junior Jet Club, I confess I found Jet! When Britain Ruled the Skies absolute bliss. The second half of BBC4's history of post-war British aviation was about passenger aircraft, and the brief but delirious period when Britain was a real player in the industry. Not everything worked: the Bristol Brabazon, a lumbering giant that had a wingspan bigger than a 747 and took 17 hours to cross the Atlantic, never got a single order. But the Comet – arriving at British airports when the passenger terminals were still army-surplus tents – was as Dan Dare as anyone could have hoped for, the future in gleaming aluminium, built right here, in sheds.

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