As a missing child, Madeleine would have once been made recognisable to the general public via simple, everyday items such as a milk carton.

Now, Kate and Gerry McCann have harnessed a far more powerful machine to alert strangers to their missing daughter: the media.

Such is the scale of the coverage that news of the British child who vanished from a Portuguese holiday resort has reached Tasmania, Singapore and South Africa; and the face of Madeleine, with her blue-green eyes framed by a blonde fringe, has now become international shorthand for parental anguish and an unsolved crime.

Eleven days since Mr and Mrs McCann’s nightmare began, the media interest has reached an unprecedented level. Pictures of the four-year-old, smiling from underneath a pink hat and looking wide-eyed and happy in an Everton football shirt, are instantly recognisable not only to those in Britain and Portugal, but to all the readers and viewers reached by the worldwide coverage.

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Paul Tuohy, chief executive of the National Missing Persons Helpline, which has received reports of 450 incidents involving missing children since the day Madeleine disappeared, said: “There has never been a case that has gained this much amount of exposure, over such a prolonged period. It is unprecedented.“In 99 per cent of cases, you have to work really, really hard to get even a fraction of the same exposure. This particular case has had worldwide media coverage. Now everyone knows her face. If Madeleine is out there, she will be sighted.

“This has captured people’s imagination because it is such an unusual case. It has picked up a huge amount of momentum, because the media have rarely come across a case like this. They will not let it go.”

However, he added a note of caution: “We just hope all the world publicity is not all used up in this one case.”

A reward offered by the author JK Rowling has secured column inches in the Chicago Tribune and Bild, the German broadsheet and newspaper of choice for many German tourists in Spain and Portugal.

Amalia Christoforou, a South African television journalist covering the story, said the news had also hit a nerve in Johannesburg: “Everybody is quite frightened by what has happened. Although abduction is not necessarily common in South Africa, there is quite a high crime rate, so people here have been following it.”

Readers of The Sun are being urged to download the missing poster and “e-mail it to everyone you know, at home and abroad”.

However, while the regular statements from her parents have helped to sustain the case of Madeleine’s disappearance at the top of the news agenda, it is the international language of football which the family have used to their best advantage.

A television plea by David Beckham, showing one of the most recognised men on the planet with a picture of Madeleine above the word “desparecida”, ensured the attention of football fans across Europe. The appearance of the Everton team sporting Madeleine T-shirts before their high profile match against Chelsea at Stamford Bridge on Saturday, boosted her profile further.

The case will find another international platform on Wednesday, when the face of Madeleine will be projected from the 24 square metre super-screen at the top of Buchanan Street, Glasgow’s busiest shopping thoroughfare, to coincide with the arrival of around 30,000 Sevilla FC and RCD Espanyol fans for the UEFA Cup Final at Hampden.

Her image will also be seen from two large screens in the central “fan zones” of George Square and Merchant City, while news alerts will be repeated on 10 public television screens in key locations, such as bus stations, across the city.

David Hodson, of the International Family Law Group, which is representing the McCann family, said that maximising media coverage had been an immediate priority.

He said: “The family, from the very beginning, have been aware of the importance of making both the public and law enforcement agencies worldwide aware of this issue.

“It must be a long time since we have seen an issue taken up in such a way. I’m told that in a number of airports around the world, people are putting up posters on their own personal initiative.”

Until Madeleine is found, Kate and Gerry McCann have no choice but to hope the world’s attention span will last as long as the search for their daughter.

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