Last Night's TV - On Hannibal's Trail, BBC4; Who Do You Think You Are? BBC1

On a magical history tour

In his magisterial tome The Seven Basic Plots (2004), Christopher Booker identified the constituents of his title as: "overcoming the monster", "rags to riches", "the quest", "voyage and return", "comedy", "tragedy" and "rebirth". Instantly, there were undergraduates gaining solid 2:1s by declaring the boundaries of these categories porous, and observing that several elements could combine within the same narrative. But sometimes, it's true, there are stories that epitomise one of these plots alone, and the virtue of last night's telly display was that it gave us a brilliant "voyage and return" immediately after the archetypal "quest".

No "quest" was as magnificent as that taken by Hannibal, a conqueror who dignified that name long before it was brutalised by first Thomas Harris and then Anthony Hopkins. Fulfilling a duty bestowed upon him by his father, Hamilcar Barca, Hannibal set off from Carthage in 218BC to become Rome's greatest enemy. The Second Punic War, also known as the Hannibalic War, was instigated by the march of his 38,000 infantry, 8,000 cavalry and 37 war elephants on Rome, via the Pyrenees and Alps. With his brothers Mago and Hasdrubal at the forefront, this giant of antiquity led what must have been one of the most glorious sights ever beheld by the human eye.

Which is why the basic device of On Hannibal's Trail seemed slightly bizarre: do the same journey, but never mind the tens of thousands of infantry and cavalry and elephants ("the tanks of the classical world"); instead, put up three Australians on their bikes, each appearing a cross between Steve and Mark Waugh, and dressed in a different pastel colour T-shirt to aid identification. And yet it worked.

Danny (journalist), Ben (IT man), and Sam (archaeologist) Wood were essentially dweeb-surfer types you see fixing roofs in the background to Home and Away, but their common adoration for ancient empires and Hannibal in particular, born of their being dragged around ancient ruins on family trips as children, gave them an authenticity that their very amateur pieces to camera added to rather than subtracted from. Cycling through mountainous terrain they seemed to be in far too low a gear, but their furious pedalling infused the whole adventure with a kind of urgency, as if their destination wouldn't wait.

Here they were at the outset, being spurred to victory by an association of enthusiasts who celebrate an annual Hannibal's Day in southern Spain; then here they were revisiting the Siege of Saguntum, a ferocious interruption to the quest further up the Iberian coast. At regular intervals we had sights familiar to all fans of Ray Mears, with night-time cameras in tents and tins of hastily composed tomato pasta. This helped to re-create the sense of their being underdogs, with the elements stacked against them as they would have been for Hannibal, but given this was only the first of six episodes, we can safely assume that greater tribulations await.

That, thank goodness, is not something that can be said of Bruce Forsyth, now in his 83rd year, and long since a stalwart of the national consciousness. Brucie has been on the telly rather a lot over the past week, but never could a show's format be more suited to its protagonist than was Who Do You Think You Are? And given how immensely popular this show is, and how familiar we are with Brucie, it may be worth elevating form above character for just a moment's consideration.

Genealogy generally makes for good telly. It's the best of "voyage and return". Marxists tend not to go in for genealogy. They think it constitutes a futile "search for identity". I've heard the argument several times. It goes: first, any form of history that elevates the individual and the local is an affront to our common humanity; second, our identities should be determined by ambitions for the future, not idle circumstances from our past. Digging around the undergrowth of our heritage is no way to discover our true selves.

This is an argument of such coruscating stupidity that its stamina in certain radical circles seems to me inexplicable. There is no logical or necessary connection between knowledge of family history and inhibition of our hopes for the future; indeed, in many cases it is a spur to success.

Genealogy places us within that conversation between the generations that distinguishes man from animal, and it's therefore particularly pleasant that an institution derided for its "cultural Marxism" should regularly stick up two fingers to the genealogy-haters. In Brucie, they had the perfect emissary from the present day. His great-grandfather was a bigamist and brilliant landscape gardener, and the pursuit of him took our hero through Mayfair to the archives of New York, and thence to a bunch of crazy women in Atlanta, and finally back home.

Having left his first wife when the fame got to him, he felt a strong association with his forebear, and over the course of an hour confirmed what we always suspected but never knew for certain, which is that Brucie's whole charm is a product of his being incredibly surprised at everything put before him. That quality is particularly amenable to this format, and as the branches of the great family tree that sprouted from Joseph Forsyth Johnson's acorn were filled with detail, the added charm of this being a rags-to-riches tale became explicit.

That, come to think of it, was one of Booker's other plots: those solid 2:1s were definitely on to something.