The two parts of the BBC's celebratory television history of the National Theatre were called The Dream and War and Peace; the second, aired last night on BBC4, re-visiting the industrial action by backstage staff that added considerably to Peter Hall's woes as he took charge of the new building in succession to Laurence Olivier and compounded his own "bad press" by moon-lighting on a television arts programme and at Glyndebourne, which he also ended up running.

There are two theories about Hall's behaviour in this period. Either, the National could only have survived and thrived, as it did, if run by such an energetic megalomaniac (Olivier, clearly, could not have begun to make the new place work); or, as Olivier's former associates Michael Blakemore and Jonathan Miller believed, the entire operation became a corrupt exercise in vanity and self-aggrandisement.

This accusation is partly true, but as the film made clear - despite opening with Hall's confession that he always got his own way as an only child as he studied scripts by a swimming pool in his back garden - his vanity was the lever to the wider success, and by the time he left, and was succeeded by Richard Eyre in 1987, the NT was truly up and running.

The brilliant appointment here was not so much Eyre's - who was seen racing along a beach on the back of a chestnut horse like a one-man cavalry charge; what was that about, exactly, apart from Richard's dashing good looks and "action man" potential? - as that of Mary Soames, daughter of Winston Churchill, as chairman of the NT board.

Appointed by Mrs Thatcher's government, this was clearly a move to close establishment ranks against the liberal insurgency Hall had instigated by putting on plays like The Romans in Britain and becoming such a fierce spokesman for subsidy in the arts, which Thatcher loathed; instead, Soames and Eyre sort of fell in love, and she in turn left the programming to him while concentrating on the first forays into sponsorship and convincing the "pinkos on the South Bank" she had been appointed to rout that commercial patronage could be as valuable as the state kind.

And so it remains today, with the natural inclination of the National to be radical and subversive where possible underpinned by city financiers and moguls such as Lloyd Dorfman, sole supplier of the Travelex cheap ticket scheme. This used to be called "repressive tolerance" in the 1960s, but I think nowadays it's more like "disinterested enthusiasm."

The two films, smartly and rather beautifully made by Adam Low, and narrated by Penelope Wilton, contained a mine of treasurable contributions. In the first one, Maggie Smith described the nimbus of untouchability that surrounded Olivier on stage ("I was petrified - I'd come from revue!"); Peter Shaffer claimed, not unreasonably, to have invented "total theatre" in The Royal Hunt of the Sun (in which, said Derek Jacobi, he wore a wig that made him look like Cilla Black); and Jonathan Miller said that literary manager Kenneth Tynan - "let's not be national, let's be international" - was a necessary irritant and an essential guide to Olivier through the sort of repertoire with which he was unfamiliar (Rufus Norris will need someone similar, if not a second Tynan, then at least a surrogate Nicholas Wright).

In the second part, Miller poured scorn on the expansionism of the NT - hard to see how that could have been avoided with the new building - and Hall's claim to be head of a "centre of excellence"; once you start using phrases like that, said Miller, you really are just revelling in your own self-importance.

One of the buried, and very sad, side-narratives in the story was the ideological split between two old friends (and close neighbours) from Beyond the Fringe, Miller and Alan Bennett. While Miller moaned and faded, Bennett moved centre stage, backing into the limelight: he launched Eyre's regime with the first ever stage representation of the Queen in A Question of Attribution (1987), himself playing the art historian and traitor Anthony Blunt. It was startling to learn that the board tried to stop the play and Eyre threatened to resign if they did, that's how controversial this commission was at the time.

The NT ended up costing £17m to build (the same figure applied to the new Hampstead Theatre, admittedly thirty years on) and now looks something like a bargain. War Horse has been the theatre's biggest success since Amadeus, which Margaret Thatcher objected to on the grounds of Shaffer's Mozart being an obscene, foul-mouthed little runt. But he was, Hall told her. Thatcher said he wasn't, because she said so, and anyway this play demeaned the National Theatre, which she cared about (but only because it was called the National Theatre; she never took the slightest interest and thought it was a Marxist revolutionary cell).

What politicians and right-wing commentators never understand is that theatre, by its very nature, and actors in their very calling, are, respectively, subversive and oppositional; good theatre is never made, as Mary Soames well understood, to placate or reinforce the status quo, family values, religious ideology or politicians.

The most interesting demonstration of this was David Hare's famous trilogy, centre-piece of the Eyre period, and Hare himself emerged as a key witness in the second film, laceratingly articulate, lauding Hall's achievement and saying he had written the plays to focus on people who spent their lives bandaging wounds in a divided society.

And just how vibrantly radical Hytner's regime has been was underlined by linking the opening Henry V (Adrian Lester's black monarch in the field in Iraq, shortly after the invasion) - brilliantly contrasted with Olivier's war-time triumphal oratory in the 1945 film - to Kwame Kwei-Armah's Elmina's Kitchen, unforgettably set in a drugs-and-violence milieu on Hackney's Murder Mile, and Peter Brook's delight in finding the experience of visiting Hytner's National, with its buzzing foyers and work on the doorstep outside, akin to going to the Globe through a market-place.

As we all gear up for tomorrow night's anniversary gala in the Olivier - I count myself lucky and privileged to have a ticket - which is broadcast live on BBC2, there's just time to acknowledge another important contribution to the literature surrounding the occasion (no sign yet of Daniel Rosenthal's "authorised" history): a reissue of Edward Petherbridge's Slim Chances.

Petherbridge's new sub-title - "NT 50: Personal, Partial, Unofficial" - is a treasure trove of wonderful stories, poems and memories of his time in Olivier's company, from playing small parts in Othello and Royal Hunt to Ferdinand Gadd in Trelawny of the Wells and Guildenstern in Stoppard's debut play; and then beyond to his participation in the Hall regime (he ran a company with Ian McKellen) and Trevor Nunn's.

He's particularly touching in conveying the downside of being an actor, the odd feeling of being lonely and undervalued in an otherwise happy ensemble, something Michael Blakemore doesn't quite catch in his own wonderful account of five years with Olivier, Stage Blood (Petherbridge had six with "Sir").

"No job gave me a stronger sense of desolation, of being nothing" writes Petherbridge, "than standing in the plainest of 17th century garb with Christopher Timothy, on Dutch Courtesan nights, waiting to lay a carpet to give Billie Whitelaw somewhere to lounge." Who'd be an actor, even at the National?