A dispute over a painting said to show King William III being blessed by the Pope is finally set to be resolved.

The canvas, depicting the arrival of William in Ireland prior to the Battle of the Boyne, has become part of Stormont folklore.

It was purchased by the old Northern Ireland government in March 1933 to hang in the newly-built Parliament Buildings.

The picture was thought to be the work of William of Orange's court artist, Pieter van der Muelen.

However, it was soon noticed that while the figure in the foreground looks like King Billy on his white charger, floating above him on a cloud is someone who appears to be Pope Innocent XI - apparently blessing Billy as he makes his way to the Battle of the Boyne.

Added to this, the man on foot in front of William's horse appears to be a Franciscan friar, complete with rosary beads. As soon as the picture was unveiled, uproar ensued, with furious unionists asking questions in the House and objecting to the Pope being shown above their revered King Billy.

In May 1933, a group of visitors from the Scottish Protestant League were touring Parliament Buildings when an enraged Glasgow councillor, Charles Forester, threw red paint over the picture.

His companion Mary Ratcliffe slashed the canvas with a knife. Both were arrested and fined £65.

The painting, which was restored, became notorious and was removed from public view.

In the BBC's Britain's Lost Masterpieces, art historians Dr Bendor Grosvenor and Jacky Klein, along with art experts from Northern Ireland, Belgium and London, discover whether the picture really does depict King Billy and whether it is even a painting of Ireland.

They also came up with some very surprising revelations about why King William III would be watched over by Pope Innocent XI.

Also in the programme, Bendor and Jacky visit the Ulster Museum to investigate what have long been regarded as low value copies of works by Flemish artist, Peter Breughel the Younger.

Painted in 1633, the two pictures show Winter and Spring and would originally have been part of a set of Four Seasons, a popular subject for Breughel the Younger, based on the work of his father, Peter Breughel the Elder. A set of all four seasons by Peter Breughel the Younger sold at Christie's this July for in excess of £6m.

The paintings in Belfast were given to the museum in 1906 by a local publican, William 'Bullseye' Braithwaite.

Although recognised during the early 20th century as works by Brueghel the Younger, doubts about the attribution were raised after the pictures were extensively 'restored' in the 1960s.

The programme uncovers whether the paintings are in fact genuine and if so, the only publicly-owned paintings by Breughel the Younger in Northern Ireland.

Britain's Lost Masterpieces is shown on BBC Two NI on Sunday at 6pm

Belfast Telegraph