“This is without doubt one of the most politically and theologically significant changes of allegiance in the Christian world for some time,” Gavin Ashenden, another recent convert to Catholicism from the C of E writes.

“There have been a number of high-profile conversions including a former Bishop of London. So why should that of Michael be so nuclear in ecclesiastical and political life?

“The answer is that he formed the centre of a nucleus of evangelical resistance to the slippage in the secular progressive accommodation embarked on by the Anglican Church. He was particularly outspoken on the serious consequences of ignoring the implications of the growth of Islam, and the importance of the Christian definition of marriage being restricted to a man and a woman with the intention of having children.”

Many of those who “swim the Tiber” are Anglo Catholics – people with similar theology to Catholics. But Nazir-Ali who left his native Pakistan as a refugee because of persecution from Islamists has been regarded as an evangelical.

Foley Beach, the Chairman of the orthodox Gafcon (Global Anglican Future Conference), writes “We are deeply grateful for Bishop Michael’s ministry over the years on behalf of the Gafcon movement.  He is a stalwart defender of Christian orthodoxy, and my own faith has been enriched and encouraged by his witness and teaching.”

Nazir Ali has left the Church of England believing it is sliding towards a progressive agenda.

“When I was ordained an Anglican priest back in 1976, it was a moment of joy, and hope: I looked forward to a lifetime in the service of God in the Anglican Church which had Christ and the Bible at its centre,” he tells the Daily Mail.

“The Church’s values were everything I believed in: helping others to come to faith and be formed by it, tolerance and freedom, the sanctity of the person, of marriage and the importance of the family. … I am deeply saddened that the Church of England is not the church I joined. There are many individual parishes, priests and believers who remain committed to biblical faith and values. But as an institution, it seems to be losing its way.”

Religion journalist Damien Thompson, associate editor of The Spectator describes the former Bishop: “A dual citizen of Britain and Pakistan, he was the Anglican Communion’s leading authority on Islam and an expert on the intricacies of Sharia and Islamic banking. He has been trenchantly critical of the British establishment’s appeasement of Muslim fundamentalists and is profoundly out of sympathy with the entrenched bureaucratic mindset of the leadership of the Church of England.”

Nazir Ali is joining the Ordinariate, a ministry of the Catholic Church designed for Anglicans with familiar liturgy. He plans to become a Catholic priest – the Ordinariate accepts married priests. Nazir-Ali is married to Valerie Cree and has two adult sons.