Behind the boarded-up windows of a derelict church in Oldham there lies a hidden treasure — and a timely reminder of Britain’s history of being a safe harbour for those fleeing persecution.

Conservationists are in a race against time to protect the stunning mural, before either the shuttered Holy Rosary Church is bulldozed and the site redeveloped, or the inclement weather takes its toll.

It’s a toss-up which comes first. But while the clock ticks, the piece of art known as The Crucifixion lies vulnerable. It was created in 1955 by the artist George Mayer-Marton, a Hungarian Jew born in 1897 and who, with his wife, fled Europe for Britain as the storm-clouds of war and the Nazi onslaught loomed.

Part mosaic and part painted fresco, it was commissioned following the Festival of Britain in 1955, and the 7.5m wide image depicts the figure of Christ in gold and tan against a dark blue cross.

A large portion of the mural had been painted over in the 1980s, and the church was closed down by t…