"So here I am - the victim of my own choices" announces Ally McBeal at the beginning of Channel Four's much ballyhooed American import. Victim? Let's tot up the damage shall we? Ally is slender, attractive, well-dressed, Harvard-educated and employed in a big city law firm. These are not characteristics that go well with any whine - and less than two minutes in Ally McBeal (10pm) seems to have set a new record - a show which has you loathing the lead character even before the credit-sequence is over. Of course - despite the effulgent syrup which the Director of Photography trickles over virtually every scene - Ally's life is not all sweetness and light. She resigns from her firm after they fail to back her up in a sexual harassment case and, though the door has not even finished closing behind her before another one opens, there is a twist - the new firm also employs her old boyfriend, a man she still loves, but who is now married to an invidiously glamorous wife.

Ally McBeal also gives a twist to television's standard realism, allowing the heroine to comment on the action as it unfolds, both verbally and by means of clips from her mental cinema. "Would you like a coffee?" asks the old boyfriend and we instantly cut to the two of them sporting naked in a jacuzzi-sized cup of cappuccino. Perhaps because these sequences are rather expensive to film they appear sporadically and not always when you might expect them. "Are you comfortable with me handling it?" asks the boyfriend at one point; given that "it" is a sexual harassment case in which Ally has had her buttocks fondled, the line is fraught with ambiguities, but the moment apparently passes without mental distraction.

Nor are such tricks novel or astringent enough to counteract the treacly self-indulgence that is the series' worst failing; but although it leaves you feeling faintly nauseated at your own sentimental gluttony, Ally McBeal does have some redeeming qualities - in particular a far less glutinous take on office relationships. There are sharp portraits of the kind of assistant who inflates her own importance with every servile update and of a winningly mercenary boss, Richard Fish. "It's not just winning, it's winning ugly that matters," he says gleefully, after entrapping Ally's harasser into a fatal confession.

One of Ally's mental commentaries is a sudden cut to her being violently sick into a lavatory bowl, an image that came into my mind while watching Diana - Secrets of the Crash (9pm, ITV), a tawdry bit of conspiracy-knitting using whatever loose ends Nicholas Owen had been able to pick up around the crash scene. Was there really anything that distinguished his report from the kind of paranoid scribble you can now find on the underpass parapet? Well Mr Al Fayed's florid autograph for one thing, a somewhat dubious endorsement which guaranteed unlimited access to the Ritz security cameras and Dodi's Paris apartment in return for a respectful interview and an account that cast doubt on the "drunken driver" theory.

The indiscriminate opportunism of the programme was epitomised by a computer reconstruction involving the "missing white Fiat Uno". One witness described a complicated sequence of events involving a powerful motorcycle and a brilliant white flash of light. Despite the fact that this had happened behind him while he himself was driving into the underpass at 60 miles per hour he described every detail of a relatively extended occurrence. On the basis of this frankly incredible testimony a computer simulation had been produced; but there was only one problem - that Fiat Uno which Henri Paul had clipped just before he lost control. The flash, it was suggested, was the result of an anti-personnel device, which would stun anybody exposed to it - "if you're driving a car when it happens you'll almost certainly crash," said Owen. And given that the Mercedes had just passed the Fiat Uno when the device notionally went off, the unknown driver would have also been exposed to its effects.

How had he avoided a second collision with the Mercedes, which was thrown directly into his path? The solution was simple - the Fiat Uno was simply made to vanish at the point where it became an embarrassment for the theory. The sequence was as fantastic as anything in Ally McBeal, but somehow not as funny.