Helen of Troy might have been the face that launched a thousand ships, but Marks & Spencer reckons Dame Helen Mirren's is the face to flog a thousand dresses.
Or quite a few more, if possible. In May, M&S posted its lowest full-year profits since 2009, a slump in clothing sales sending pre-tax profit down 6 per cent to £665.2m.
Now the 129-year-old high street stalwart has dumped its "faces" of the past few years, Twiggy and Myleene Klass, and instead splashed out on the fashion photographer Annie Leibovitz and a campaign featuring "Britain's Leading Ladies". The retailer's new clothes horses are the artist Tracey Emin, Brick Lane's author Monica Ali, the Olympic boxer Nicola Adams, creative director of American Vogue Grace Coddington, the ballerina Darcey Bussell, supermodel Karen Elson, singer Ellie Goulding and the charity campaigner Katie Piper, as well as Dame Helen.
Marks & Sparks' gathering won't come cheap. And it might not even succeed, according to Tony Quinn, chief strategy officer of the advertising giant Publicis. "Celebs can work very well for brands – they give glitter and fast-track brand recognition," he said. "But it all goes tits up when a brand that's struggling to find its way says 'let's grab a celeb to fix sales'.
"That's happened with Morrisons and Ant and Dec, and there's a bit of that feeling about M&S too – a sense of, 'we're not quite sure what we're about, so we'll try to be something for everybody'. It's a scattergun approach to building a brand – chuck enough celebs at people in the hope that something will hit."
So how do you choose a face for your brand? There are two ways, according to Ralph Scott of the brand agency CDW & Partners, whose clients include M&S. First there is "brand reinforcement – picking personalities that align with what a brand already stands for", and second there is "brand repositioning, as M&S is doing, where you try to use celebrities to take the brand in a direction where it's perceived in a different light.
"By picking Annie Leibovitz [a photographer for Vanity Fair], M&S is moving in baby steps to try to secure more of a high-end fashion focus."
Importing the kind of Hollywood glamour captured by Ms Leibovitz is another big trend in advertising, according to Richard Thompson, head of the talent division at the ad agency M&C Saatchi. "A lot more Americans – serious Hollywood A-listers – are doing ads over here than, say, five years ago, like Kevin Bacon for EE [the mobile phone group], Al Pacino and Jennifer Aniston for Sky," he said. "Brands are looking for a very big sledgehammer to crack a walnut, and they want to break into multiple territories, so they're going for the big guns."
Elsewhere, the mobile giant HTC has a new campaign featuring Robert Downey Jr, and Jean-Claude Van Damme is flogging Coors lager. The stars are clearly doing it for the money, but, Mr Thompson added, "they also see the UK as a far-off territory. Would Pacino do that kind of ad in America? Probably not, but he feels OK doing it here. Taking the talent away from their main territory means they don't get diluted."
There can be a problem with picking a well-known face for your brand, however – what the industry calls the "Lance Armstrong issue" but could also be applied, lower down on the notoriety scale, to Tiger Woods. "You're held horribly hostage to the behaviour of that celeb," said Mr Quinn at Publicis. "That's great when Lance is clearing up on the Tour de France, but not so good when he's tangled up in a doping scandal."
Brands try to protect themselves against the risk of their name becoming tarnished through association with the personal life of a celebrity with "death and disgrace" clauses – warranties against bad behaviour. "M&S's use of multiple celebrities mitigates against some of the potential issues," said Joseph Petyan, an executive partner at the ad agency JWT London. But it could also create other problems: "With competitor brands such as Littlewoods employing their own raft of celebrities, one can't help but wonder how distinctive and differentiated this approach is. One thing is for certain: celebrity is no substitute for a proper brand idea."
Certainly, celebrities and brands are not always compatible. "The biggest mess was John Cleese for Sainsbury's," said Neil Saunders, the managing director at the retail analyst Conlumino. The Monty Python and Fawlty Towers comedian was filmed shouting loudly about cheap offers, but "the supermarket had previously prided itself on quality," Mr Saunders pointed out. "Cleese's anarchic yelling about cheap deals actually hit sales. The supermarket chose him to be a face of their brand in a bid to be a bit irreverent and wacky, but customers saw Sainsbury's as more serious, middle of the road." The ads were noticed in the City. They were referenced in analysts' notes. Shares fell. Mr Cleese was axed.
So watch out, M&S, and don't get too reliant on your stars either. "It overwhelms the message," said Mr Quinn. "I did a lot of work with David Beckham and Adidas. He began by being the face of a particular boot, the Predator, which was all about precision, and Beckham's glorious goals from the halfway line meant he was the perfect expression of the brand. But eventually, I think Beckham became bigger than Adidas."
Perhaps M&S should have opted for a cheaper solution –one that would negate the possibility of the face of a brand being embroiled in a drugs scandal, or becoming so successful that fees soar. "Pick a meerkat," said Mr Quinn, "it won't get involved in a scandal. And it's a lot easier to negotiate on fees with a meerkat."
The perfect model? It's Kate Moss
From her 1993 ad for Calvin Klein's Obsession to this year's St Tropez fake-tan campaign, Kate Moss has been probably the most in-demand face for advertisers in modern times.
Even being photographed apparently about to vacuum a line of cocaine up her nose in 2005 only dented demand for her services temporarily. So what is the pull?
Brandon Leigh, the finance director at St Tropez owner PZ Cussons, says his team had specifically wanted to push the lotion into the fast-growing markets of Brazil and the US as well as Europe, where it was already established.
The supermodel was one of the few faces famous and cool enough in all of those countries for the campaign to work: "Kate is an international star," he says. Editors, recognising their audience's appetite for "anything Kate" gave acres of coverage to the St Tropez brand in glossy magazines, newspapers and TV shows, from Rio to New York City to Berlin. The fact that she posed naked added to the editorial allure, of course. Sales in Brazil and the US spiked instantly.