It's late 1994 and a group of advertising executives from brand agency Abbott Mead Vickers BBDO are considering a PepsiCo brief for a one-off advert to reposition Walkers crisps. They hit upon the idea of an ad that shows the crisps as so tasty they turn a normally nice celebrity into a thief. "How about Gary Lineker?" says one executive. "He's a nice guy and he used to play for Leicester (where Walkers is made). Let's pick him." And they did.

It may not have been that simple, but however the decision was made, it paid off. Who would have thought that 12 years and 55 TV adverts later, Lineker would still be Walkers' front man, having helped sell an extra 1.4 billion bags of crisps a year and double sales to £2.75bn in seven years.

Predicting how successful a celebrity endorsement will be is about as easy as picking a Grand National winner. But as the Walkers example demonstrates, if you get it right the rewards can be rich. But how do companies work out which star has potential and who is going to bomb?

This is the question Asda, Tesco, Walkers and Kellogg's have been asking recently. All four companies have just launched high-profile celebrity-led campaigns using well-known faces such as Ian Wright, Martin Clunes, Monty Panesar and Paul Whitehouse. How have they realised their decisions? And are they the right ones?

Picking the most expensive celebrities is no longer a sure-fire route to success. Indeed, all these companies are eschewing high-profile stars such as Wayne Rooney and David Beckham for personalities with a closer affinity to their brands. Beckham may once have been the celebrity every company clamoured for to endorse their brand. He even appeared in an ad at a supermarket checkout, though he was promoting Vodafone. But his glamorous image, and the fact that he endorses many, very different products, means that he doesn't convey the serious messages these companies are increasingly aiming for.

Nowhere is this more evident than in the latest spate of celebrity endorsements for Asda, which have far greater emphasis on what the person stands for than how well they are known.

"Sharon Osbourne failed to hit the mark because there was no way the average Asda consumer could relate to someone with millions of pounds," says Melinda Henley at recruiter Ellis Fairbank.

Coming under threat from the farming lobby for squeezing suppliers, and under attack in other quarters due to its image as a soulless cog in Wal-Mart, Asda has dropped its iconic price-led 'pocket patting' adverts for a series of fly-on-the-wall-style campaigns that show Victoria Wood working on the shop floor and Paul Whitehouse visiting milk suppliers. These ads speak for a much greater affinity with what Asda is trying to say, says Henley. "Down-to-earth comedians such as Whitehouse and Wood are a great match for Asda, which has a no-nonsense approach. Consumers can relate to them because they are seen as normal people, but at the same time they are funny."

It is not only companies that are becoming more canny about how a celebrity ties in with a brand. Consumers are also more aware of who they think should be linked with a certain company, says Deborah Carter, innovations expert at branding agency Dragon Brands. "Consumers have a clearer idea of what a brand is about and who they associate with it. Companies are investing in more research to find out what that connection is."

This is why Coleen McLoughlin, girlfriend of Rooney, has been equally successful for Asda. Unlike Osbourne, people believe Coleen could shop at Asda. "She is the girl next door, someone who the George consumer can relate to," says Henley. "Coleen is a famed shopaholic and consumers believe she would not have a problem wearing George clothing."

Possibly the cleverest use of celebrities in recent months has been Kellogg's Wake Up To Breakfast campaign. Kellogg's is fighting negative messages about its cereals and has chosen three very different people to convey three very different messages.

The celebrities in question - Jo Frost, better known as Channel 4's Supernanny, footballer Ian Wright and Tomorrow's World presenter Philippa Forrester - are used on-pack to talk about fighting obesity, the lack of performance if you skip breakfast and the nutrient content of cereal.

"There are two ways to use celebrities," says marketing director Kevin Brennan. "You can use those who you pay to advertise your brand or those who actually believe in the message you want to get across. Consumers are looking for credible celebrities so Jo Frost is a great personality to emphasise the importance of child nutrition. Ian Wright is a well-known sports personality who appeals to adults and children and has campaigned against childhood obesity, so he brings credibility to the campaign. It is these types of people who consumers trust that are the most effective at getting our message across."

This is why Sainsbury's use of Jamie Oliver has proved so successful. Its tie-in with the chef is estimated to have generated an extra £1bn of sales - and some £200m profit - in the first two years alone. "He's down to earth but aspirational and appeals to middle England," says Henley. "He is a great match, probably much more than Sainsbury's even realised."

Few could have imagined, when he first fronted its adverts in 2000 as a lovable 'mockney' chef with bags of enthusiasm, that he would, through choice, become so closely aligned with Sainsbury's core values. Now a family man, his campaign to improve school dinners and his restaurant Fifteen, which has helped underprivileged school leavers get a job in the food industry, have helped raise his and Sainsbury's profile.

Of course, not all celebrity endorsements have such lofty aims. Walkers' and Tesco's recent campaigns also carefully use celebrities in a more conventional way. In Tesco's case, Clunes continues the retailer's use of TV personalities that simply have a lovable, yet slightly quirky image. Previous faces it has used include Noel Edmonds, John McEnroe and Prunella Scales.

Walkers' use of Panesar is even more straightforward. The Sikh cricketer follows a long line of sports stars promoting grocery brands. As well as being an obvious choice to launch a campaign aimed at the UK's Asian community, his enthusiasm and achievement as a spin bowler have won him plaudits and popularity across the nation.

While Panesar looks like a squeaky clean choice, however, it is not always easy to predict how a celebrity will behave. Take Kerry Katona. The mother of three has been the face of Iceland since 2004 and seemed an inspired choice to front a TV campaign aimed at young mums after she won the TV show I'm a Celebrity Get Me Out of Here. Indeed, she was initially a huge success.

More recently, however, she has been dogged by tabloid stories of drug-taking. Iceland wouldn't comment on the impact Katona's tabloid appearances of late have had on the Iceland brand, but tellingly this summer's campaign only features her as a voiceover. Irish singers the Nolan sisters are fronting its ads instead.

Some companies are still prepared to take the risk. PepsiCo, for example, uses personalities such as Charlotte Church and Tara Palmer-Tomkinson - well-known for their wild parties and outspoken views - but places confidence in them, says Jon Goldstone, vice president of marketing at Walkers. "We knew Charlotte Church was someone who spoke her mind, but that's why people love her." As to Lineker, adds Goldstone: "He knows it would cause embarrassment if he was photographed eating another brand of crisps but we don't police him." Like Oliver, who admits to buying groceries in independent shops and whose wife Jools has been caught shopping at Waitrose, the jug-eared pundit has the Teflon touch. nWayne Rooney

Likeability ?

Fame factor ?

Can we afford him? ?

Clean reputation ?

Paparazzi potential ?

Face for TV ?

Part of a good celebrity couple ?

Appeal to an adult age group ?



Gary Lineker

Nice guys don't always finish last as Walkers discovered when Lineker was picked as its front man. He has boosted sales by some 1.4 billion packs a year.

Britney Spears



A multi-million dollar deal with Pepsi didn't stop Spears from being snapped drinking a can of Coke. And then - oops, later that year she did it again.

Ian Botham



Who'd have thought the wild man of cricket would be endorsing healthy cereals? On TV since 1981, Botham has had a great innings, however.

John Cleese



Sainsbury's 1999 Value to Shout About ads, starring Cleese, remain a horrible reminder of how endorsements can backfire. More faulty than Fawlty.

Coleen McLoughlin



Famous for shopping and dating a footballer, Coleen also has girl-next-door appeal. Better still, she was 'Asda price' according to Andy Bond.

Vinnie Jones



The hard man couldn't deliver the hard sell for Bacardi and his reported £120k deal was put on ice after a drunken fight on a plane in 2003.

Stephen Fry



The quintessential Englishman with refined tastes has proved to be the perfect face for this British staple and has helped raise sales of Twinings.

Sharon Osbourne



Does an LA living woman married to a rock star really shop in Asda? The public certainly didn't believe so and very soon the retailer realised this too.

Paul Whitehouse



Asda has hired The Fast Show comedian to star in its latest round of fly-on-the-wall documentary-style adverts. The ads feature Whitehouse on the milk round with one of Asda's suppliers, cracking jokes and generally making a nuisance of himself as part of the retailer's campaign to show the people behind its products. The adverts have so far proved popular and have even spawned a spoof version using its outtakes, which is currently circulating the internet.

Jo Frost



Channel 4's Supernanny manages to tame even the most recalcitrant of children by sorting out their diet as well as their behaviour. She is now being used to teach children the benefits of a healthy breakfast. Frost, alongside footballer Ian Wright and Tomorrow's World's Philippa Forrester, is fronting Kellogg's Wake Up to Breakfast campaign, which espouses the virtues of breakfast. She adds credibility to the campaign, according to marketing director Kevin Brennan.

Monty Panesar



Walkers wanted to target the cricket-loving Asian community in the UK for the launch of its Chilli & Lemon variant, and there seemed no one better to front its campaign than Monty Panesar. Panesar, England's first Sikh cricketer, has shot to fame for his deadly bowling but also follows in the footsteps of Walkers' long-term front man Gary Lineker as sport's other Mr Nice Guy. He is being used in a targeted campaign with adverts featuring on Asian radio stations and in events.

Martin Clunes



Clunes, who is best known for his role as goofy Gary in the sitcom Men Behaving Badly and more recently in the ITV drama Doc Martin, is part of a long line of TV personalities used by Tesco for its lighthearted ads. Starring alongside Fay Ripley he features in the retailer's latest advert for its Localchoice milk. The ads have so far courted the limelight for the wrong reasons, however, after supermarket campaigners questioned Tesco's definition of local.