ONE of the most important areas of medieval stained glass in the world has been restored to its former glory after ten years of painstaking work.

Experts believe the St William Window at York Minster now looks much as it did when it was new in the early 15th Century after the ground-breaking treatment.

The huge window, 23.78m tall and 4.8m wide, depicts in 105 main panels the miracles of St William of York, including what is said to be the only miracle attributed to him that took place during his lifetime.

In the middle of the 12th Century, when St William returned to York as archbishop, a crowd gathered on the then-wooden Ouse Bridge, which collapsed under the strain - but no one was hurt as St William blessed the crowd.

The window in the North Quire Aisle was finished by 1414 and, over the centuries, has been mended many times, using lead that gradually obscured its beauty.

But for the past ten years, it has been largely hidden from view while expert Dr Christopher Norton carried out extensive research and the panels were worked on by craftsmen from York Glaziers Trust.

Their skills have been used to remove many of the heavy lines of previous fixes.

The research and new techniques are now expected to prove invaluable for the planned restoration of the Minster's Great East Window - the largest expanse of medieval glass in the world.

The Dean of York, the Very Reverend Keith Jones, said: "This is an epoch in the art of conservation. The huge window as restored is amazing, and sets the scene for the even greater challenge of the East Window. It shows what we can do."

The Dean and Chapter plans to celebrate the completion of the work with a series of events timed to coincide with St William's Day on June 8.

St William - born William Fitzherbert - was treasurer of York Minster from 1112 to 1114. He was consecrated Archbishop of York in 1143, deposed in 1147, but reinstated in 1154. He died the same year. The cult of St William grew during the 1200s as pilgrims visited his tomb and reported miraculous healings.