Once more to a familiar furrow, stardust-seekers, as Lost in Showbiz asks the sub-rhetorical question: what do you reckon about "documentaries" like Peaches Geldof on Islam? "Finding a celebrity who genuinely cares about the issue really helps pull in a crowd that wouldn't otherwise switch on," is the view of BBC controller Danny Cohen. "But you have to be careful. If you get a rent-a-celeb, this audience can spot it a mile off."

Mm. Spotted 50 miles off - lumbering knickerless over the horizon - comes Ms Lindsay Lohan, whom you might recall was BBC3's somewhat leftfield pick to explain the issue of child trafficking in India to its audience.

Contemplating the hire, this column fell back on that old cliché about Lindsay not even being able to get arrested in Hollywood, which was technically wrong, as Lindsay has been arrested for a high-speed late night car chase and possession of class A drugs, among other CV highlights. Still, suffice to say her diary was sufficiently "freed up" for her to jump at the chance of caring about the trafficking issue and stuff, and the Beeb have been forced to defend her involvement ever since.

Lindsay Lohan's Indian Journey - like BBC3 say, it's not about her, it's about the issue - finally airs tonight. But by way of a curtain raiser, and thanks to assistance from the likes of Unicef and a BBC source close to the production, Lost in Showbiz has been able to piece together the totally heartwarming story behind Lindsay's "journey".

To India, then. As I say, the documentary is about the issue of child trafficking, and the production company's plan was for Lohan and the crew to be in situ for a planned raid by Indian authorities (with the aid of a charity), ensuring she was there for the rescue of a number of children who had been trafficked and placed into forced labour.

After protracted negotiations, Lindsay agreed to do this, so first class flights were booked for her, her bodyguard, and her assistant. Meanwhile, the crew travelled to India and waited for Lohan to make her entrance. At this point, according to a BBC source, the hokey cokey one might have regarded as inevitable started, and Lindsay began backtracking on her commitment, causing flights to be repeatedly cancelled and rebooked as she kept producers in the dark as to her plans. Alas, despite myriad ignored messages, she failed to pitch up in India before the raid, which went ahead without her in a way that, say, a Roberto Cavalli fashion show would never dare to.

It was at this point that Lindsay took to Twitter, in tweets later described by the BBC as "misinterpreted". "Over 40 children saved so far," read one of these communiqués. "Within one day's work ... this is what life is about ... Doing THIS is a life worth living! Oh, and I'm talking about being in India."

Mm. Intriguingly, Lindsay was not even in India at the time these messages were tweeted - a fact on which BBC3 declined to comment, saying only that police raids are not scheduled. On the contrary, say local police and magistrates - the raids had been planned for two months and Lindsay's implication that she was there was somewhat resented. "We'll be complaining to the BBC and talking to our lawyers," a leading social activist and lawyer, who was organisationally involved with the raids, fumed to the Daily Telegraph. And for a bit it looked as if the Indian mission might be just another of Lindsay's nice ideas that she never quite got round to (see also a mooted trip to Iraq with Hillary Clinton, and some African mercy mission with the Red Cross).

However, Lindsay finally agreed to travel to India, arriving the day after the raid. According to a BBC source, the cost for acquiring three last minute first class travel tickets was by now in excess of £30,000, though the BBC press office say this figure isn't correct and that anyway the film was delivered by the production company at a fixed cost. They do not dispute the fact that they knowingly allowed her to travel without a work visa, a decision which might now see Lohan blacklisted from travelling to India.

Still, once in India, by all accounts Lindsay behaved obligingly, though whether you regard her spending no more than two and a half days in India justifies the title "Lindsay Lohan's Indian Journey" is a matter for you.

Thereafter, though, things began to fall apart once more.

Realising a serious treatment of the subject would require Lindsay engaging with a serious authority on child trafficking, the producers worked to set up a filmed interview between her and Unicef in New York. Despite some rumoured misgivings about the choice of celebrity advocate, Unicef agreed. Lindsay having also agreed, a camera crew was duly dispatched to New York ... and once again, the hokey cokey started. Indeed, despite repeated entreaties to Lindsay to reconfirm she would be honouring her obligations on this issue about which she professes such passion, Lindsay's studied vagueness continued right up to the minute of the meeting, whereupon Unicef confirm to me that madam stood the lot of them up.

Why? Well, the magic of the internet allows us to establish that Lindsay was disporting herself at Milan fashion week at the time. Here she is with Roberto Cavalli.

In the end, hasty arrangements were made for her to ask the questions of Save the Children in London, and in the documentary a partied-out looking Lindsay can be seen doing that before suggesting people should help via "Twitter? There's Twitter ... "

As for the documentary, you must judge it for yourself, but having seen a preview DVD of it I second my colleague Amelia Gentleman's assessment that the most excruciating moment comes after a very young street beggar from Calcutta tells Lohan her story.

Over to Amelia's account:

The shaven-haired girl is explaining that her parents would beat her unless she went out every day to earn money, but it's hard to concentrate on what she's saying because what's happening behind her is so distracting. Lohan is rubbing her already-red eyes, spreading mascara around the place, twitching her eyebrows. "Um. Um. Oh my God," the film star says, her lips wobbling uncontrollably. A disembodied hand pops into the screen to pass her a tissue. "Um. How did she feel? Um. How did they treat her?" she asks, beginning to sob. The small girl turns to look at her in bemusement. The translator gives an embarrassed laugh and says to the girl: "She's crying for you. Why don't you comfort her?" So we watch as the puzzled child dutifully strokes Lohan's long mane of golden hair. "Oh my God! Oh my God!" Lohan says, with a husky gasp. "Sorry, I'm having a moment." Mercifully, the camera is then switched off. One could write thousands of words about the matter, but in that single vignette is distilled everything that is arse-about-tit about this level of celebrity-led documentary.

So what have we learned from l'affaire Lohan? I guess the question is: does it really matter if, behind the scenes, the so-called talent behaves like a real piece of work, as so-called talent has been wont to do since time immemorial? I am afraid I would have to say it doesn't, within reason (and within reason I include a fair amount of financial wastage) - but if, and only if, what ends up on the screen justifies the means. For instance, I don't care what horrors Joan Crawford and Bette Davis were on the set of Whatever Happened to Baby Jane: it ends up being a cracking film.

However, if what you're making isn't a high camp movie but a documentary about child trafficking, and your famous trainwreck star keeps genuine experts from fronting such films, and your end product features a scene in which a very young and serially abused child labourer is required to comfort a Hollywood starlet, then it would seem fair to cast the production as such an obvious moral failure that it's worth anatomising the wrongheaded decisions that led to such a flawed idea being aired - and wondering if they are not symptomatic of a wider cultural malaise.

The puzzle is that all of this could have been avoided if BBC3 hadn't indulged in such ludicrous casting. After all, it's not as if Lindsay is merely rumoured to be a flake. Lindsay is known to be a cast-iron, copper-bottomed, A-list flake. Indeed, her utter flakery is so well documented that there exists on public record an extraordinary letter to Lindsay from the CEO of Morgan Creek, the studio that produced the last major film with which she was involved (it might become evident that the two are connected).

"Dear Lindsay," begins this notorious blast from James G Robinson.

Since the commencement of principal photography of Georgia Rule, you have frequently failed to arrive on time to the set. Today, you did not show for work (all day). I am now told you don't plan to work tomorrow because you are "not feeling well." You and your representatives have told us that your various late arrivals and absences from the set have been the result of illness; today we were told it was "heat exhaustion." We are well aware that your ongoing all night heavy partying is the real reason for your so called "exhaustion." We refuse to accept bogus excuses for your behavior. To date, your actions on Georgia Rule have been discourteous, irresponsible and unprofessional. You have acted like a spoiled child and in so doing have alienated many of your co-workers and endangered the quality of this picture. Moreover, your actions have resulted in hundreds of thousands of dollars in damage. We will not tolerate these actions any further. If you do not honor your production commitments, including your scheduled call time for tomorrow, and any call times thereafter, we will hold you personally accountable. This means that in addition to pursuing full monetary damages, we will take such other action as we deem necessary to preserve the integrity of the Georgia Rule Production as well as Morgan Creek's financial interests. I urge you to take this letter seriously and conduct yourself professionally.

That, my ducks, is how serious people treat talent that is taking the piss. That the rubes at BBC3 apparently felt unable to do so is a shame, but we can only hope they think twice before commissioning the next demographic-insulting "journey". At least let us get into 2011 before Kerry Katona's Darfur Odyssey hits the schedules.