Yet this almost accidental prime minister, elected three days after the Madrid bombings, has emerged in the past two years as a surprisingly powerful leader, and he sits comfortably in an office that itself is a political statement: the floors are stripped bare, the desk is more architect than politician and a Miró stares confusedly down at him — it is Ikea meets Tate Modern.

He is one of a generation of European politicians of the Left who has drawn inspiration from the electoral successes of Tony Blair, but foreign policy differences have put distance between them. Señor Zapatero’s first political act was to withdraw Spanish troops from Iraq and the disagreements have proliferated as quickly as issues have arisen. While, in public, Mr Blair has been sympathetic to Israel’s policy in Lebanon, Señor Zapatero has been openly critical, describing the Israeli offensive as an abuse of force.

Where he does depart from the more predictable positions of the European Left is over the fate of Mexico, a country whose democratic future still hangs in the balance after an election two weeks ago whose results are still disputed.

Señor Zapatero has already called to congratulate the centre-right candidate (Felipe Calderón), who has officially won that election. Now he says that he is “absolutely” ready to ring the left-winger (Andrés Manuel López Obrador), who is taking his case to the streets, unnerving a Spanish leader whose own country returned to democracy only three decades ago.

“I’m convinced that the PRD [López Obrador’s party] will accept the final constitutional ruling,” Señor Zapatero says. “The essence of democracy is accepting the rules of the game, even if you lose by a very small margin. You can always win the next elections. And you can always do a lot for your country from the opposition. A good opposition paves the way for a good government.” Mindful of the rise of the Conservative Party in Britain, he quips: “This has nothing to do with the Opposition in Britain. It’s just a general comment."

Like Mr Blair in his early years of government, Señor Zapatero is putting his energies into tackling one of the most intractable conflicts in the country’s history. After the announcement of a permanent ceasefire, his Government has begun controversial talks with Eta, the Basque terrorist group responsible for about 800 deaths in more than three decades and sometime partner of the Irish Republican Army.

“In my opinion we have the best opportunity to see the end of [Eta’s] violence and terrorism,” he says. “We will be working very cautiously and discreetly. They were two pieces of advice that Tony Blair gave me. And I’m trying to be very disciplined. But it will take time. The history has been one of a great deal of pain.”

The Prime Minister is also vigorously promoting the devolution of powers to Spain’s regions. He gambled in campaigning for greater autonomy for Catalonia, the region around Barcelona, and set a precedent for Spain’s other “autonomous communities”.

The conservative Opposition accuses the Prime Minister of presiding over the break-up of the nation, a possibility he dismisses. “I’m a firm believer . . . of bringing power closer to citizens,” he says. “Those who criticise me in Spain say that the State has very little power. Nevertheless, they are still very intent on recovering it. It’s a total contradiction — they know it’s not true. There is no risk of fragmentation.”

The Prime Minister has also angered the Roman Catholic Church in Spain by introducing liberal social measures, including fast-track divorces and same-sex marriage, and he has scrapped a measure by the previous conservative Government to make religious instruction in schools compulsory. Hence, for the Church, Señor Zapatero has become the patron saint of secularism, but the Prime Minister suggests that the priests should not blame the Government if Spaniards are increasingly turning away from institutional religion.

“It is the people who decide whether they have more or less religious vocation. It is religious denominations who have to analyse why they have more or less followers,” he says. “I believe that spiritual values are not only religious values. I think that modern-day democracy has very ingrained values, very spiritual values, such as peace, solidarity towards those who need it the most.”

Both his language and his frenetic legislative activity have infuriated conservatives, who had expected to win the 2004 election and remain convinced that the explosions which took 192 lives just before the election were too sophisticated to have been the work of a motley collection of Islamic extremists, and so must have been, in some unspecified way, the handiwork of Eta.

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