The announcement of Martina Navratilova's inclusion in the squad for this year's I'm a Celebrity ... Get Me Out of Here! sent shock waves through sport yesterday. Not only in the world of tennis are people asking themselves: “Why?”

The statistics don't lie. Eighteen grand-slam singles titles. Thirty-one grand-slam women's doubles titles. Ten grand-slam mixed doubles titles. Her legacy is complete. Her fortune is made. Her professional reputation is unassailable. She didn't fall out of a boy band three years ago. She hasn't been in panto since 1992. No matter how you do the maths, the nine-times Wimbledon singles champion lacks the hair-trigger neediness that has tended to define the archetypal I'm a Celebrity contestant down the years.

Some even wonder whether there has been a misunderstanding among Navratilova's people about the nature of the show. Do they know about the boxes of rats, the platters of kangaroo parts? Shades of 2006, when Traci Bingham, the American actress who used to appear in Baywatch, declared it “truly an honour” to have been invited on to Celebrity Big Brother. A lot, one reflected, can get lost between here and the other side of the Atlantic.

Or maybe Navratilova knows exactly what she is doing. Maybe this is the eternal battler rising to another challenge, seizing the chance to record a triumph on the one surface on which victory eluded her during that improbably lustrous career - damp earth. And I'll say this much: I can think of no one from the women's game that I would rather have alongside me in a testicle-eating contest. With the possible exception of Billie Jean King. But that's just a pipedream.

One thing is certain. Of all the sportspeople to have pulled on the coveted I'm A Celebrity sleeping-bag, Navratilova is the first bona fide, undisputed, top-ranking star. Phil Tufnell, who gloriously snatched victory out of the camp-fire in series two, was a former England cricket international, true enough. But you wouldn't say he bestrode his sport. He sat around on the edge of it, smoking, maybe. But he didn't bestride it. Similarly, Nigel Benn, the boxer, who lasted for about five minutes in series one, knew glory in the ring. But his was not the kind of globe-girdling fame that Navratilova brings to the camera-infested clearing.

Which of the show's 2008 cast comes anywhere near her orbit? Not Robert Kilroy-Silk, that's for sure. Nor Esther Rantzen. Nor that token bloke from EastEnders. In terms of international penetration, only Mr Sulu from Star Trek has earned the right to pull up a camp-bed alongside Navratilova.

As ever at this time of year, one is left ruefully pondering the might-have-beens. In advance of the official declaration, all sorts of people are said, tantalisingly, to be “in the frame”. Accordingly, one struggles to suppress disappointment that the rumour linking Graham Poll, the retired football referee, with a place at the camp-fire turned out to be false.

The sight of Poll returning in triumph from a Bushtucker Trial, having retrieved eight stars secreted somewhere about an emu, could have had a positive knock-on effect for the “Respect” campaign. But, sadly, it was not to be - though analysts agree that it can only be a matter of time before the “Thing from Tring” enters the reality television arena, perhaps in the slightly less hostile environment of Hell's Kitchen. It'll be him or Jeff Winter, bank on it.

And what happened to Chris Eubank? Only a month ago the bookmakers were radically shortening the odds on the lisping cavalier's participation in Australia, only for him to be nowhere in the final reckoning. Perhaps that's for the best, though. Eubank would have been hoping to rely on his fistic wiles, but the laws are different in the jungle, where a boxer is likely to float like a butterfly, get stung by a bee. (See Benn, above.)

As it is, the 2008 list boasts a dominant WAG theme. Carly Zucker is the fiancée of Joe Cole, the Chelsea midfield player. Nicola McLean, who used to have a column on page 3 of The Sun, is engaged to Tom Williams, the Peterborough United midfield player. And Dani Behr, the television presenter, once had trials with Ryan Giggs, of Manchester United.

The WAG lifestyle has come in for some serious knocks recently, what with the global economic downturn and with Rio Ferdinand blaming the likes of Michaela Henderson-Thynne for losing the World Cup in 2006. An emphatic jungle-based performance from one of the above could silence the boo boys, clear out some of the opprobrium that unfairly surrounds hangers-on and give a much-needed boost to the idea of fame by association.

Zucker, in particular, is definitely fit. And I mean that, first and foremost, in the aerobic/gymnastic sense that the word has now all but lost. But is she fitter than Navratilova? That's the question that is set to have the nation agog as the coming series unfolds.