The chattering classes are aghast. Whatever made her do it? Why, oh why, is Germaine Greer demeaning herself as a feminist heroine by appearing on that ghastly reality show Celebrity Big Brother, with a bunch of contestants whose brains, my dear, must have the cutting edge of a rotten banana?

One critic confessed to being left shaken at the “shock horror” appearance last week of the 65-year-old professor of English literature and author of The Female Eunuch amid the likes of Brigitte Nielsen, the Amazonian former wife of Sylvester Stallone, the model Caprice and John McCririck, the racing pundit.

Flabbergasted misses the point. The most pertinent question is why Greer didn’t opt for the rival series I’m a Celebrity . . . Get Me Out of Here!, whose jungle camp is based near her Australian property in Queensland. There, in her native clime, she could demonstrate her extensive knowledge of plants, cooking, the rainforest and snakes.

But isn’t her appearance on Big Brother’s 18-day orgy of bad taste a touch hypocritical? After all, Greer has written: “Watching Big Brother is about as dignified as looking through the keyhole in your teenage child’s bedroom door.” She added: “Reality TV is not the end of civilisation as we know it; it is civilisation as we know it.”

No one who has studied Greer’s form would hold her to that. She has spent the past 40 years doing the opposite of what was expected of her, no matter how many U-turns it might entail. Children are a burden, she wrote in The Female Eunuch. A few years later, she declared they were a joy. Sex is a weapon in the female struggle against oppression, she asserted. Later she retracted, saying women might be better off without it.

The former stunner — who counts among her lovers George Best, Martin Amis, Julian Barnes, Jonathan Aitken, Warren Beatty (whom she apparently found disappointing) and the late John Peel (who claimed she forced him to have sex) — now advocates celibacy.

By offering Greer large sums of money to enter the Big Brother house, the producers evidently expect her to have the same galvanising effect as Janet Street-Porter in the recent I’m a Celebrity.

She might, with luck, undergo a psychological meltdown like Vanessa Feltz, the journalist. But the hope is she will unleash some of her lethal verbal invective. She called Victoria Beckham “a starved carnivore” and described the writer of her unauthorised biography as “flesh- eating bacteria”. In a broadside addressed to Tony Blair after Cherie suffered a miscarriage, she said: “She’s 47 years old, she doesn’t practise contraception because she’s a Catholic — stay off her.”

Greer reserved her most venomous put-down for Suzanne Moore, her fellow columnist on The Guardian, after the latter commented on an inaccurate report that Greer had had a hysterectomy at 25. Greer accused her of having “hair birds-nested all over the place, f***-me shoes and three inches of fat cleavage”.

Still, squandering such ammunition on C-list celebrities ranks with mauling dead sheep. What is really in it for her? Money is important: Greer always demands top rate so she can finance rainforest rehabilitation on her Australian estate, although this time her chosen charity is Buglife, the invertebrate conservation trust.

She is also an unashamed exhibitionist. Her late-night performances on Newsnight Review have failed to reach the masses. Fortunately, her penchant for grabbing the headlines has allowed her to transcend such restricted forums. Some of her neighbours in Essex choked when she called on them to embrace an expansion of Stansted airport. There was also an outcry and accusations of encouraging paedophilia when she confessed that she loved looking at pictures of “ravishing” young boys.

Sales of her book The Boy soared.

By coincidence, just as a heated national debate began on crime and trespass in the countryside in 2000, she became front-page news when she was held hostage in her home by a teenage student who had become obsessed with her, crying “Mummy, Mummy” until the police arrived.