ITV1’s forthcoming drama, Rock Rivals, will feature an ending chosen by public vote: it’s Strictly Come Drama Idol Academy by Shed Productions, maker of Footballers’ Wives and more. There’s more about it on BBC News Online where, incidentally, you will see that NOL’s picture budget isn’t what it was: they have a shot of star Michelle Collins, but it’s a library one of her with a Dalek.

Anyway, I’d like now to do the Critic’s Trick.

It goes thisaway. I haven’t seen a single frame, I haven’t read the script, I don’t know the story, and still I’m going to say to you that both endings will be poor. Or, put it another way, neither will work.

You can call this harsh and I wouldn’t disagree. But don’t think it’s anything against Shed. As it happens, I don’t believe there’s been a Shed show that grabbed me but I think that’s just chance: I like the firm’s chutzpah and the lick it has to its writing. I hope Rock Rivals works. You always want a new drama to work. I just don’t think this one will.

And this is why. The two endings.

This is always presented as an exciting new idea, every time it loops around, but it’s predicated on the assumption that you can have two endings. That the ending is a module you buy in later. Instead, I’m pretty sure you’ll agree, the ending is part of the whole: a story, even the most formulaic and predictable, is an organic piece that is building to its ending. Just look at that word: predictable. Even though you might not want a piece to be predictable, part of the reason that it becomes so is that every inch of the tale is pointing in one way.

When a story has enormous shocks along the way, they are usually very effective but they only stay with you, they only truly work when in retrospect they’re no surprise at all. I think of this like rubbing your hand over a piece of wood: go one way, against the grain, and you’re getting shards of wood cutting in to you, drawing blood, and yet rub your hand back the other way and it’s perfectly smooth. Just blood-stained.

So if you build a piece in order to drop in one of a number of endings, either the story doesn’t naturally point to that ending or it does point to the moment before the change. It’s common to see the penultimate episode of a series being the very best one, just because endings are so tough, but abdicating the ending feels like giving up before you start.

Or how about an example? There was a recent episode of Lewis where I happen to know the ending was changed very late in they day; ITV wanted another twist before the last commercial break or something. I’m not sure what, really, but I know it was changed and when you watch it I swear you can tell the point when it switches tracks.

Two weeks ago I’d have harrumphed now and gone back to work with a so-there. But while I feel as strongly as I ever did about this insert-ending-here approach, I do now have an example that at least suggests I’m wrong. So I’d best tell you, hadn’t I?

What if a show could legitimately build to two endings, simultaneously? Whichever was aired, we’d feel the absence of one of them but at least the one that was shown would work. I’m not convinced it’s at all possible, but hold that thought. Now, what if a show’s ending changed not only what you thought of its beginning but really changed the beginning? If a late decision coloured the start of a story in a way you didn’t expect and the makers didn’t intend?

It’s happened with Doctor Who. Forgive me if you haven’t seen the end of the latest series, and if you need to look away now just promise me you’ll agree I’ve made a great point. Toward the end of the final episode, we learn that Captain Jack Harkness is the Face of Boe.

I found that inexpressibly sad. I don’t know why: I liked Boe, I like Jack, I was just deeply saddened. And by chance, I caught an earlier episode on UKTV Gold the other day, the episode in which we first see Boe. He’s just a figure in the background, he’s really almost a joke: he enters with a parade of other startling aliens.

And all I could think of throughout the episode was how the Face of Boe must feel, seeing the Doctor and Rose.

It really made the episode better, but I know the Boe/Jack idea wasn’t in place until a little later.

So maybe you can twist a beginning by changing the end. But I’ll still bet money that Rock Rivals won’t work.