A rare book believed to have been used to convert an English king to Catholicism has gone on public display.

The copy of the Missale Romanum, or the Roman Missal, was owned by Father John Huddleston, who helped to save the life of King Charles II and had the book with him when the monarch converted to the Catholic faith on his deathbed.

A missal is a book containing prayers offered by the priest at the altar as well as everything that is read or sung in connection with the Mass throughout the ecclesiastical year.

The book, published in 1623, was purchased by the National Trust at auction and will be put on display at Moseley Old Hall, near Wolverhampton, 363 years after it was first there.

It contains Fr Huddleston’s signature and even drops of candle wax on some pages.

It is also crucial for our understanding of how Roman Catholic books were used and circulated at a time when it was dangerous to be anything other than Anglican.

Tim Pye, national curator at the conservation charity, said: “The Huddleston Missal is a wonderful acquisition for Moseley Old Hall. Not only is the 1623 edition of the Missale Romanum a rare book – just one other complete copy is recorded in UK libraries.

“It is also crucial for our understanding of how Roman Catholic books were used and circulated at a time when it was dangerous to be anything other than Anglican.

“The way in which Huddleston has inscribed and annotated his missal highlights just how precious and personal this book would have been to him.”

Fr Huddleston was a Benedictine priest who lived at Moseley, dressed as a servant and protected by the Whitgreave family, who were Catholics and remained loyal to the Royalists’ cause following the execution of Charles I at the end of the English Civil War.

During the Anglo-Scottish War, also known as the Third English Civil War, from 1650-52, Charles II’s royalist forces were defeated by Oliver Cromwell’s Parliamentarians, eventually forcing the monarch into exile.

Following the Battle of Worcester in 1651, Charles famously hid from Parliamentarian troops in an oak tree on the grounds of Boscobel House in Shropshire, before fleeing to Moseley the following night.

He was there given shelter by Fr Huddleston and shown to a priest hole beneath a cupboard floor when armed troops arrived at the house looking for the king.

The bed on which Charles slept remains at Moseley today, and he consulted several books – including the missal – in trips to Huddleston’s library.

Displaying and interpreting the missal will provide a compelling focus and renewed impetus for telling the story of Charles II’s remarkable escape.

Following Charles’ restoration, Huddleston was made chaplain to the King’s mother, Queen Henrietta Maria, and later his wife, Catherine of Braganza.

As Charles lay dying in 1685, Huddleston heard the King’s confession, administered the Eucharist and received him into the Catholic Church.

The missal was previously owned by Joseph J Procter, who paid a Liverpool bookshop just sixpence for it, in the late 1950s, before being purchased by the National Trust.

Sarah Kay, cultural heritage curator, said: “We’re delighted to have secured this important book which is central to the story of Moseley.

“If we hadn’t acquired it, it is likely to have gone into private hands and not been accessible by the public.

“Displaying and interpreting the missal will provide a compelling focus and renewed impetus for telling the story of Charles II’s remarkable escape.”