By Robert Pigott BBC Religious Affairs correspondent

The Pope's tour of the Americas is being followed by the BBC's Robert Piggott. In the first in a series of diaries, he reports on celebrations in Toronto to mark World Youth Day

Roman Catholics in Toronto had braced themselves to greet a frail old man.

But Pope John Paul II took them by surprise when he arrived at the airport and made his own way down the aircraft steps onto Canadian soil.

He glided across the tarmac on the mobile platform propelled by Vatican officials.

The new vehicle made its first appearance last Easter, when the Pope's Parkinson's Disease and arthritis at last made it impossible for him move about unaided.

Tens of thousands were present at the festivities

But, as so often before, the Pope seemed to gain fresh energy from celebrating Roman Catholicism with young people. He smiled and waved, looking stronger than he has for some time, even pausing to milk the applause from the crowd.

Chants of "We want the Pope!" and "John Paul we love you" rose up.

But the Pope's message was a serious one - about rejecting the temptations that a secular and commercial world presents.

Speaking in French, he said "Dear young people, many and enticing are the voices that call out to you from all sides. Many of the voices speak to you of a joy that can be had with money, with success, with power. Mostly they propose a joy that comes with the superficial and fleeting pleasure of the senses."

Challenging the Church

The Pope devised World Youth Day to enhance the image of the Church in the eyes of young Catholics. But it was also intended to remind them that to believe in Jesus Christ is to accept everything he said.

In his main address in Toronto, he told Catholics they could not simply pick the bits of the faith they liked best and reject those they found awkward.

But many young Catholics are not prepared to accept that they must follow the Pope's conservative line - even on central issues such as abortion, birth control and the role of women in the Church.

Many found the ceremony an emotional experience

Some have made their opposition to papal authority far more strident. A group called Challenge the Church is in Toronto to protest against John Paul's hard line on contraception.

They were getting on well, handing out condoms to everyone filing into the exhibition centre - until they tried to give one to a Canadian nun.

"You'll answer for your actions," she told the demonstrators.

Unmistakeable enthusiasm

Unhappiness about the Pope's hard line on issues such as celibacy and the role of women in the Church are being blamed by some people for a lower than expected attendance in Toronto. Around 200,000 people registered for the whole five days - fewer than for any previous World Youth Day.

However the organisers said that almost twice that number turned up to welcome the Pope.

Their enthusiasm was unmistakeable. Many were moved to tears. They shouted and sang, and held the flags of dozens of nations above their heads.

But affection for the Pope does not always translate into obedience.

Scandals over sex abuse have damaged the church in North America and, increasingly, ordinary Catholics feel bold enough to follow their own consciences.