A 20-year investigation into the life and works of Fr Ignatius Spencer has been approved by Vatican historians, it emerged yesterday.
The document, known as a positio, has now been passed over to theologians of the Vatican Congregation for the Causes of Sainthood.
If they decide there is “evidence of sanctity”, they will then ask Pope Francis to declare the Victorian Passionist priest as “Venerable”.
At that point, the Catholic Church will begin the search for two miracles needed first for his beatification – when he will be given the title of “Blessed” – and then his canonisation, when he will be declared to be a saint.
Fr John Kearns, the British Passionist Provincial, described the development as a “step down the road” to sainthood.
He said: “The positio has been finished and finalised and has been submitted to Rome and has got through the historical commission and is now going to the theologians.
“We would invite people to pray that the sanctity of Fr Ignatius Spencer can eventually be recognised by the Church.”
Princes William and Harry are related to Eton-educated Fr Spencer through their mother Diana, Princess of Wales.
Members of the Spencer family, he was her great-great-great uncle and also a great uncle of Winston Churchill.
He was given the name George when he was born in Admiralty House in 1799, the youngest son of the 2nd Earl Spencer, the First Lord of the Admiralty.
He grew up at the Spencer family home at Althorp, Northamptonshire, where Lady Diana was buried after she was killed in a Paris car crash in August 1997.
As a child he would have met such people as Lord Nelson, Sir Joshua Reynolds and Isambard Kingdom Brunel who were regular visitors to the family home.
But he turned his back on a life of immense wealth and comfort by converting to the Catholic faith – a move which horrified his contemporaries.
He later joined the newly formed Passionist order, and was ordained priest under the name Fr Ignatius of St Paul.
He ministered among Irish migrants in the West Midlands and people so poor that they lived in caves dug out of slag heaps.
The priest also took advantage of the rail network that was being laid out by the Victorians to travel widely throughout Britain to preach missions.
He died from a heart attack in 1864 while he was walking through Scottish countryside to visit a cousin.
Church scholars say Fr Spencer was about 150 years ahead of his time in his quest for Christian unity.
He has been credited with “preparing the ground” for the ecumenical movement of northern Europe in the late 20th century.
Fr Kearns said: “He was always asking people to pray for Christian unity. The expression he used was ‘unity in the truth’.
“The mainstream thing (among Catholics) would have been ‘everybody convert to Catholicism’,” he said.
“He wasn’t against that and had done that himself but he could see that something else was needed and that was his objective.”
In spite of his absolute commitment to his faith Fr Spencer retained a great love for cricket, which he described as “my mania”.
He often organised matches among the servants of his household as a young man and later, while serving as Dean of St Mary’s Seminary in Oscott, Birmingham, he taught students for the priesthood also how to play.
His body is entombed in the Church of St Anne and Blessed Dominic in St Helens, Merseyside.
He lies beside Blessed Dominic Barberi – the Passionist priest who received Blessed John Henry Newman into the Catholic Church in 1845 – and Sister Elizabeth Prout, the “Mother Teresa of Manchester” and founder of the Passionist Sisters whose cause for sainthood has also been opened.
Bishop Mark Davies of Shrewsbury said: “I am sure Catholics welcome the progress of the cause of Fr Ignatius Spencer recalling a heroic and often neglected chapter of the story of the Church in this land.”
He added: “In facing the challenge of secularism Fr Ignatius and his fellow Passionists – Blessed Dominic Barberi and Mother Elizabeth Prout – remind us of the missionary energy and purpose which marked ‘the second spring’ of the Catholic Church in England.”