Amy Jenkins: Why must a woman's sexual capital be the key to her worth?

When it comes to older women in the public eye, it seems only two types are successful: those who do a passable imitation of youth and therefore don't count as old, like Madonna, and those who are honourable exceptions to the rule, like Maggie Smith; the rule being No Wrinkly Ladies on Screen, Please and the exceptions being very rare.

If you've made it to being an exception, you've probably also made it to being a dame.

However, if you're the 53-year-old presenter of a BBC show called Countryfile, you haven't got a hope in hell. Miriam O'Reilly was just that – and despite being exceedingly presentable and good-looking, despite having won awards, having built a following, and having an impressive body of journalistic experience, she was dumped unceremoniously when the show was "refreshed" (how Orwellian) in 2008 and replaced by a 38-year-old. Her fellow presenter, John Craven, who is 68, was not replaced. Presumably because he is exceedingly presentable, has won awards, has built a following, etc, etc.

O'Reilly is now suing the BBC for sex and age discrimination and told the court this week that she was told by her director that she would have to "be careful about those wrinkles" when high definition TV came in. She also claimed that it was recommended to her that she use Botox and hair dye. A cameraman on the show called her a "rare species" in the world of television. Sadly, as Arlene Phillips, 66, was dropped from Strictly Come Dancing a few months later, I'd say that the word extinct was probably a better description. Meanwhile, Bruce Forsyth goes on and on, as do David Dimbleby, David Attenborough, Jeremy Paxman, Jon Snow, Noel Edmonds – the list is endless.

It is no coincidence that just as the menopause strikes, women are deemed to go past their on-screen sell-by date – "sell" being the operative word here. A woman's worth in our patriarchal consumer economy is dependent on her sexual capital, her ability to seduce and reproduce. The sexist system both makes her redundant (in the broad sense) – and then can't bear to contemplate her because of that very redundancy. If those are your fiduciary terms, an ageing woman can only remind you of death – and worse, the pointlessness of the entire enterprise. It is the bane of a good capitalist's life – the fact that you can't take it with you.

Fitting, then, that it's probably the marketplace that will save the middle-aged TV presenter and bring her back to our screens. Because the truth is that times are changing and the BBC has been getting it wrong. There was a genuine and heartfelt outcry when Phillips left Strictly and I'd bet good money the BBC regrets the decision. Now there are rumours that she will return. This doesn't surprise me when the past few years has seen the movie Mamma Mia!, which starred Meryl Streep at 60, become a worldwide box-office smash, to say nothing of the unlikely Susan Boyle – paean to dumpy middle age – taking the music business by storm.

Until this small revolution it was thought that even middle-aged women didn't want to look at middle-aged women, but this has turned out to be completely untrue. This year, we love Ann Widdecombe on Strictly and Mary Byrne on The X Factor. What's more, with our ageing demographic, following the money is going to mean catering to the tastes of a larger and larger elderly population. And guess what? Like everyone else, they want to see themselves on telly.

What you realise, as you get older, is that most young people are really quite boring. Like wine, TV personalities tend to get better with age. Wouldn't everyone far rather listen to a slightly weatherbeaten, richly experienced woman who's seen a bit of life, than a fresh-faced young beauty who doesn't know she's born?