Long forgotten drawings in a Victorian sketchbook could prove the key to recreating an ancient high cross that once guarded St Patrick's grave.
The sketches showing how the cross once looked when it stood on the Hill of Down were found by Carrickfergus man George Rutherford in the Public Records Office of Northern Ireland.
They provide clues which will help experts at Down County Museum to piece together the remains of what could be one of the most ancient high crosses in Ireland.
Three remaining fragments of the cross have long puzzled experts, but curator Mike King and his colleagues have turned detective in a bid to solve the mystery. He began to search for early images and was approached by George Rutherford who had found a drawing of St Patrick's Cross dating back to 1843 in a scrapbook of sketches by Alexander Johns of Carrickfergus.
Then expert Peter Harbison identified another drawing of the cross, dating to about 1840, in a collection of drawings put up for sale in Dublin.
Together the old drawings reveal that the cross was damaged some time before 1840, losing its cross-shaft and having its top arm knocked off.
It was also vandalised in 1842, and was eventually broken into the three sections which now survive inside Down Cathedral.
The museum enlisted the support of Dean Henry Hull, the Friends of the Museum and the Downe and Lecale Historical Society to have the surviving fragments of the cross conserved by Cliveden Conservation.
Cleaning uncovered intricate interlace, key and spiral patterns on the fragments which could pre-date the Downpatrick high cross by 100 years, and make St Patrick's Cross one of Ireland's earliest high crosses.
Archaeological reconstruction artist Philip Armstrong will create drawings of what St Patrick's Cross may have looked like.
One square fragment decorated with spiral designs may have been the top arm of the cross, knocked down to leave a T-shaped cross by 1840 and later used to prop up the remains of the cross-head, as shown in the drawing of 1843.
The museum says it may be possible to scan the fragments and use the information to create a replica of the cross to stand at St Patrick's Grave, where the original was a focus of veneration until the 1840s.
Down County Museum's Medieval Mystery Tours which are being staged this summer will include a visit to the newly conserved cross.
Tickets can be booked from Down County Museum, on (028) 4461 5218.
St Patrick's Cross may have stood more than 4m tall, with a 1.6m cross-head. It was not supported by a ring which may have made it vulnerable to damage, and was probably why later high crosses were carved with the ring around the cross-head. It seems to be an early prototype, perhaps influenced by wooden high crosses, and without the relief figures of scripture crosses.