The mystery thief of some of the rarest maps in the world has been unmasked after a worldwide investigation by Spanish police that led them to Britain, Australia, America and Argentina.

Spanish detectives flew this weekend to Buenos Aires after a man there admitted to stealing up to 19 valuable maps from a collection held at the Spanish National Library, some more than 500 years old.

The discovery in August that the cream of the Spanish cartographic collection had been stolen sparked a political storm that cost Rosa Regàs, the Catalan writer who was head of the National Library, her job. It also led to accusations against the Government that it had been cavalier with the nation’s priceless historical artefacts.

Now the new head of the library says that the country is within days of regaining the stolen maps, which had been snapped up by collectors and shipped around the globe. “I am very happy,” said Milagros del Corral, who has been charged with reinforcing security at the library, in Madrid. “I think we are seeing a light at the end of the tunnel.”

César Gómez Rivero, a Uruguayan-born Spanish citizen who is said to have lived in Buenos Aires for several decades, sent his lawyer to negotiate an immunity deal with an Argentine judge last week in exchange for handing over eight of the maps. “He is full of remorse because he involved people he knew and abused their confidence,” Fernando Soto, his lawyer, said.

The judge refused the deal, placing the maps in his vault but releasing Mr Gómez on bail. Spanish authorities are seeking his extradition to stand trial in Madrid, where penalties for the theft of historical items are much stiffer.

Acting on requests from Spanish police, the FBI has retrieved another map from Richard Lan, a dealer in New York, who had sold it to a private client. Australian police have recovered another from Simon Dewez, a dealer in Sydney, who bought it in America. Both men insist that they bought the maps in good faith.

“I had absolutely no idea it was stolen,” Mr Dewez said. “I thought it was a fantastic buy, a rare opportunity.” The self-confessed thief was a map expert who was able to enter the Cervantes Hall, where they were kept, with the aid of a researcher’s pass. Mr Soto explained that, after several years working at the library, his client had “realised that he could evade security controls and take the originals. That’s what he did, and he managed to leave without being seen.”

Using a Stanley knife, Mr Gómez cut at least ten pages from centuries-old books, including two world maps from 1482 editions of Ptolemy’s Cosmo-graphia, valued at £50,000 each.

World view

£7m raised by Library of Congress to buy the 1507 Waldseemuller map, the first to use the term America

700 years approximate age of Mappa Mundi, one of most important medieval maps, held in Hereford Cathedral

£1.5m value of maps stolen from Harvard and elsewhere by the map dealer E. Forbes Smiley III before his arrest in 2005

Sources: American Libraries Association; Hereford Cathedral; www.vintagemaps.com

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