He played a pivotal role in the collapse of Communism, but to critics he is a dictator who has helped spread misery and disease.

As Pope John Paul II marks 25 years as the head of one billion Catholics, Nick Morrison looks at the impact of the most recognised man in the world.

ARRIVING at a familiar airport less than eight months after his election, the robust figure in white walked slowly down the steps of the Boeing jet and, on reaching the bottom, immediately knelt down and kissed the tarmac. Pope John Paul II had come home.

It was a visit which was to have enormous and far-reaching ramifications, and not only because it was the first visit of a Pope to a Communist country since the end of the Second World War. By returning to his Polish homeland, John Paul II set in motion the chain of events which was to lead to the collapse of a political system.

As his convoy took him from the airport to Victory Square in the centre of Warsaw, more than two million people lined the route, and when he held his first open-air mass it was to a congregation of one million. "You are men," he told them, "You have dignity. Don't crawl on your bellies."

That nine-day visit in June 1979 was the catalyst which led to the creation of the trade union Solidarity 15 months later. That, in turn, was the spark which engulfed the Iron Curtain and freed Eastern Europe from Communism. According to Mikhail Gorbachev: "Everything that happened in Eastern Europe would have been impossible without the presence of this Pope."

It is 25 years ago tomorrow that Cardinal Karol Wojtyla (pronounced Voy-tee-wah) became the first non-Italian Pope since the Dutchman Adrian VI in 1542. The crowd of 200,000 in Rome's St Peter's Square was initially stunned on hearing the news, but when the new Pope abandoned tradition and addressed them in Italian instead of Latin, they erupted into wild applause.

His election, which came after two days and eight ballots in the conclave of cardinals, was seen as a victory for the Third World cardinals who wanted a non-Italian pontiff, but the new Holy Father's first action was to take the name John Paul II, in honour of his predecessor Pope John Paul, who died after only 33 days in office.

At 58, John Paul II was the youngest Pope for 132 years, but he was a reluctant successor to St Peter. He turned up late for the final conclave and almost missed it, and while the cardinals indulged in their power struggles, he was found reading a review of Marxist theory in the Sistine Chapel. When another cardinal congratulated him on his election and said there was sure to be great jubilation in Poland, the new Pope replied: "Yes, but there will be none in Wojtyla".

Karol Wojtyla was born in 1920 just outside Cracow, the son of a retired army officer. When he was nine, his mother died giving birth to a stillborn daughter, and three years later an older brother died, but the young Karol remained stoical in public, telling a teacher: "It is God's will".

When the Nazi occupation closed his university campus, he worked as a labourer in a stone quarry and chemical factory, developing a strength and robustness which was still striking when he became Pope. He worked for the underground, helping Jewish families to safety and putting his life in danger every day.

Deciding to study for the priesthood, he went to an underground seminary, and was ordained a year after the war ended. Rapid promotion saw him become a bishop at 38, Archbishop of Cracow at 44 and a cardinal at 46, before his elevation to the Papacy 12 years later.

His visit to Poland in 1979 was the first in what was to become a hallmark of his Papacy. With more than 170 visits to over 115 countries, he is the most travelled Pope in history, and his habitual kissing of the ground on arrival ensured him instant adulation. His globetrotting and efforts in the cause of peace - he has frequently spoken out against dictators and provided inspiration for their overthrow - earned him nomination for this year's Nobel Peace Prize, although the prize was to elude him, much to the disgust of his supporters.

His pace was only temporarily slowed by the assassination attempt in May 1981, as he blessed the crowds in St Peter's Square. He was hit by four bullets, two of which lodged in his intestine, almost killing him. After his recovery, he visited his would-be killer, Mehmet Ali Agca, in prison and forgave him. For his next foreign visit, John Paul II appeared in a bullet-proof car, immediately dubbed the Popemobile.

But while his visits have earned him enormous affection and made him the most recognised man in the world, there are those to whom he is not the benign baby-kissing old man. While, to some, his steadfast pronouncements are a welcome constant in an era of spiritual vacillation, to others he has imposed his beliefs like a dictator, regardless of the human suffering which may result.

John Paul II has been unbending in his denunciation of abortion and contraception, refusing to compromise even in the face of the spread of Aids throughout sub-Saharan Africa, and despite evidence that European Catholics are ignoring his advice, notably in staunchly Catholic Italy, which has the lowest birth rate in Western Europe.

He has been similarly dogmatic over priests remaining celibate and refusing to countenance women priests, putting growing links with the Anglican church at risk and despite a dramatic fall in the number of candidates for the priesthood in the West over the last 20 years.

And throughout his Papacy, John Paul II has been ruthless in quelling theological dissidents. Within a year of his election, he had expelled Hans Kung from his post of professor at the Catholic university of Lucerne for the crime of progressive thinking, making him just the first in a long line of troublesome theologians who were given short shrift.

Under his leadership, debate has been stifled in the Catholic church and Papal infallibility firmly imposed. Roma locuta, causa finita (Rome has spoken, the case is closed) has become the refrain. At the same time as taking the Catholic faith across the world, he has erected a wall of unyielding dogma around the church.

But while he has alienated many liberal Catholics, and the Church is even losing followers in his beloved Poland, John Paul II has had more influence on world events than any Pope since the Renaissance and the number of people entering the priesthood in the Third World is at record levels. While the West turns away from such rigid certainties, in Africa and Latin America such conviction is something to hang on to in a harsh world.

It is only in recent years that the once vigorous Pope has started to succumb to the advance of old age, although it is just two years since his doctors acknowledged what had become widely known: that the Pontiff has Parkinson's disease. Uncontrollable shaking and unsteadiness, missing his weekly public audiences and an inability to kneel to kiss the ground have given fuel to fears that his end is fast approaching.

If the Pope is indeed as frail as he appears, he can at least be confident his legacy will be assured. Having appointed more than 90 per cent of the cardinals who will choose his successor, John Paul II can reasonably expect the next Pontiff to be in the same mould. But while that may have been appropriate to see off European Communism, whether it is suitable for the rather different demands of the 21st century is another matter.