TELEVISION / The Royal flush of embarrassment: Mark Lawson watches Diana - Her True Story on Sky One and finds that one is very much amused

Those who favoured publication in Britain of the 'Camillagate' tape often pointed out the social inequity that - because of the availability to those with faxes of transcripts from Australia - the chattering classes had easy access to material that was denied the ordinary punter. The latest Royal scandal - the four-hour mini-series Diana: Her True Story, which concluded on Sky One last night - levelled the score. Given the uneven social dispersal of satellite dishes, the working classes had unrestricted access to material the upper classes were denied. What did those without dishes miss? They missed the hoot of the year. Will the series - as Lord Deedes has suggested - further damage the Royal Family? I think the drama may have the opposite affect, by belittling through association the serious piece of popular journalism on which it was based: Andrew Morton's book of the same title.

The distinction of Morton's volume was that its larger allegations about the marriage of the Princess of Wales and her unhappiness within the Royal Family were not the usual anonymous nudges, but were attributed to relatives and friends. In contrast, the main sources for the tone and approach of the television version seem to have been American television soap operas, a genre prominent in the previous experience of producer Martin Poll and director Kevin Connor. That neat mid- Eighties tabloid coinage 'Pallas' - employed when events at the Palace began to resemble those in Dallas - reached its apotheosis here.

Princess Diana (Serena Scott Thomas) was the Sue Ellen: an unloved lovely with refulgent eyes and a substance abuse problem, though in this case food rather than booze. Every soap opera needs its deviant psychological behaviour and the bulimia was really made a meal of. If Kenneth R Thorne's soundtrack for the series were ever released as a record, it would certainly include a sequence called 'Lavatory Theme', a boiling orchestral hubbub which prefaced the actress's crouch-runs to the lavatory bowl after supper. There would also be 'Rottweiler's Theme', a look-out yelp of string instruments for the appearances of Camilla Parker-Bowles (Elizabeth Garvie), music reminiscent of that used for the entrances of the evil Kristin in Dallas or Alexis in Dynasty. Camilla, a horsy good sort, spoke solely in equine dialogue, bow-legged with innuendo: 'Charles loves to ride . . .We ride together all the time.'

True to the television template it had chosen, Diana: Her True Story treated the line of Royal succession purely as a business understanding. Shown in an early scene expressing a wish that her son would succeed her while young, the Queen later reneged: 'I have decided, Charles, there will be no change at this time.' It was an encounter exactly analogous to Miss Ellie's frequent changes of mind over her dispersal of Ewing Oil shares in Dallas. In the same line of descent was the splendidly risible moment in which Prince Charles - listening to the Queen's 1991 Christmas broadcast, in which she hinted at an intention to reign until death - hurled his drink into the fire and yelled: 'Bloody Hell]' I trust that Andrew Morton, who made so much of the solid factual provenance of the original book, feels some unease about the attachment of his name to such a series, not just as source author, but as 'adviser'. It must be assumed that his advisory powers were as cosmetic as those constitutionally given to the Queen.

There are two things you look for in a drama based on real events. These are credibility of impersonation and authority of dialogue. In the first area, a majority of the cast of Diana: Her True Story would have benefited from name badges. Either I had gone mad by the final credits or Prince Edward really was played by an actor called Crowd-Double, but few of these doubles would have stood out in a crowd. Early on, you kept thinking that the Queen was unusually chummy with her butler, until she called him 'Philip' or 'The Duke'. Serena Scott Thomas played Diana on a wig and a prayer, but the match was so imperfect that her husband's laments about 'having married the wrong woman' took on a dark new possibility.

Anne Stallybrass as Queen Elizabeth had taken the original, if historically eccentric, decision to model her performance on Marlon Brando in The Godfather. Helped by the director's tendency to frame her in deep shadow at a desk, she was a female Corleone with a crown: a scowly-jowly mater familias who took no shit from anyone and put a threatening stress on the words 'The Family'. Andrew Parker- Bowles was a silent man with a big dog. Surrounded by performances less Spitting Image than What's My Line?, David Threlfall's Prince Charles was all the more remarkable. His creation was a precise verbal and visual photocopy, down to the Novocaine-frozen mouth, the sniff, cheek-suck and nose-rub. Threlfall deserves an award for, as it were, keeping his face while all around him were losing theirs.

As for authority of dialogue, Stephen Zito's script had three strategies. The first was the join-up-the-back- numbers approach, ransacking the tabloids so that his Prince Charles was always talking about how his rhubarb liked a good natter. The second was, for the Queen, a sort of Robert Boltish rhythmic-archaic prose, Zito having read that historical bigwigs refer to themselves in the first person plural: 'How could you take our position as Head of the Church? The bishops would not tolerate a divorced monarch.'

Zito's third technique was to fold in the best quotes from Morton's book, and, here, he achieved an interesting effect. One trick of writing drama based on fact is to inject the text with direct historical quotation, the realities solidifying the inventions around them. In this case, the made-up phrases were often so preposterous as to make the real ones seem improbable. For example, one critic has already giggled at the comment given by Zito to one of the princess's sisters when she threatens to cancel the Wedding Of The Century: 'Too late now . . . your face is on the tea-towels.' But this was plausibly presented in Morton's book as an authentic line. Similarly, the celebrated 'Squidgy' phone-call sounds wholly bogus when recreated in the drama while, on the existing tape, it is credible banality.

The producer of Diana: Her True Story, Martin Poll, was previously vaguely known for his film The Lion in Winter. Poll has neatly linked that monarchic project to his present one: 'In many ways this is the sequel to The Lion in Winter . . . (but) instead of the Plantagenets, it's the Windsors.' Poll, however, is missing one important distinction. By the time he got round to the Plantagenets, they were long dead, with a weight of existing histories for him to draw on. Diana: Her True Story suggests that, had he chronicled them contemporaneously, their subsequent reputation might have been significantly different. Richard III, for example, would have been a comedy.

I doubt that John Major - in his strenuous attempt to quieten the sense of crisis surrounding the Royals - will have been gladdened by the screening in Britain of this depiction of the institution which he apparently still reveres. I hope that he and his ministers appreciate the irony that the terrestrial broadcasting system which they have denigrated and deregulated would almost certainly have retained enough Reithian deference and high-mindedness not to have screened the mini-series. It was the newly-admitted satellite channel of Rupert Murdoch which chose to disoblige the nobility. But then the last few weeks - with the screening of the Dennis Nilsen interview, the beaming in of satellite porn from Amsterdam and, now, Diana: Her True Story - have shown the government and its electors just what free- market television means.