Pope Benedict XVI has begun his four-day visit to Britain with a warning against “aggressive forms of secularism” that are failing to tolerate traditional values.

Addressing the Queen and other leaders, including the Archbishop of Canterbury and Deputy Prime Minister, the Pope spoke of the "Nazi tryanny that wished to eradicate God from society and denied our common humanity to many, especially the Jews".

He said: "As we reflect on the sobering lessons of the atheist extremism of the twentieth century, let us never forget, how the exclusion of God, religion and virtue from public life leads ultimately to a truncated vision of man and of society and thus to a 'reductive vision of the person and his destiny'."

The Pope spoke of his desire to "hold out a hand of friendship" to British people.

He urged them to live by the values of “honesty”, “respect” and “fair-mindedness” and warned them not to forget their Christian heritage.

“The Christian message has been an integral part of the language, thought and culture of the peoples of these islands for more than a thousand years,” he said.

“Your forefathers’ respect for truth and justice, for mercy and charity come to you from a faith that remains a mighty force for good in your kingdom, to the great benefit of Christians and non-Christians alike.”

He continued: “Today, the United Kingdom strives to be a modern and multicultural society.

“In this challenging enterprise, may it always maintain its respect for those traditional values and cultural expressions that more aggressive forms of secularism no longer value or even tolerate.

“Let it not obscure the Christian foundation that underpins its freedoms.”

Thousands of people lined the streets of Edinburgh today to catch a glimpse of the Pope in his famous white Popemobile. Protestors who had planned to express their opposition to the visit could barely be seen amid the throngs of people waving Scottish flags and flags bearing the face of the Pope.

The Pope flew into Scotland this morning for the first official state visit made by a pontiff to Britain and the first visit by a pope since John Paul II made a pastoral visit in 1982.

In her welcoming speech, the Queen spoke of her appreciation of the Holy See’s involvement in improving the situation in Northern Ireland and its “important role” in international issues, supporting peace and development and addressing common problems like poverty and climate change.

“Your Holiness, your presence here today reminds us of our common Christian heritage, and of the Christian contribution to the encouragement of world peace, and to the economic and social development of the less prosperous countries of the world.

“We are all aware of the special contribution of the Roman Catholic Church, particularly in its ministry to the poorest and most deprived members of society, its care for the homeless and for the education provided by its extensive network of schools.”

The Queen said the visit would provide an opportunity to deepen the relationship between the Roman Catholic church, the Church of England and the Church of Scotland.

She went on to say that the relationship between different faiths had become a "fundamental factor" in cooperation within and between states.

"It is therefore vital to encourage a greater mutual, and respectful understatnding," she said.

"We hold that freedom to worship is at the core of our tolerant and democratic society."

The Pope flew in Edinburgh International Airport this morning, where he was greeted by the Duke of Edinburgh and senior Catholic leaders, including the head of the Roman Catholic Church in Scotland, Cardinal Keith O'Brien.

He will travel to Glasgow today for an open-air mass at Bellahouston Park, before flying to London tonight. He will hold another open-air mass in Hyde Park on Saturday and end his visit on Sunday with an open-air mass in Birmingham’s Crofton Park to beatify John Henry Newman.