An artwork displayed at a Norfolk stately home has been identified as a rare surviving work by a printmaker credited with inventing colour printing. 

It had always been believed that a copy of the Sir Anthony van Dyck portrait the Three Eldest Children of King Charles I, displayed at Oxburgh Hall, near Swaffham, was oil on paper. 

But now the artwork at the National Trust-owned moated estate has been found to be a rare print by 18th century printmaker Jacob Christoff Le Blon after it was sent away for conservation treatment at the charity's Royal Oak Conservation Studio in Kent.

Eastern Daily Press: The copy of the Sir Anthony van Dyck portrait the Three Eldest Children of King Charles I, displayed at Oxburgh Hall in Norfolk The copy of the Sir Anthony van Dyck portrait the Three Eldest Children of King Charles I, displayed at Oxburgh Hall in Norfolk (Image: PA)

The German-born painter and engraver, who died in 1741 aged 73, was the first to create a three-colour printing process – the forerunner of the CMYK colour printing used today.

His method used mezzotint – a monochrome printmaking process – with separate plates inked in blue, yellow and red and superimposed on one another to create an endlessly variable depth of hue.

Until then, artists had inked colours one beside the other on a single printing plate.

Eastern Daily Press: Oxburgh Hall, in Kings LynnOxburgh Hall, in Kings Lynn (Image: PA)

Jane Eade,National Trust curator, said van Dyck’s portrait was “much copied” but “only three Le Blon prints of it were known to survive”.

“To have discovered a fourth is really exciting, especially as it is the only version that remains hanging in its historic setting,” she said.

Analysis of the piece helped identify the colours Le Blon is known to have used, such as indigo and carmine or red lake.

All of the versions were hand-coloured after printing.

Eastern Daily Press: Inspecting the copy of the Sir Anthony van Dyck portrait the Three Eldest Children of King Charles I, displayed at the National Trust-owned Oxburgh Hall in Norfolk Inspecting the copy of the Sir Anthony van Dyck portrait the Three Eldest Children of King Charles I, displayed at the National Trust-owned Oxburgh Hall in Norfolk (Image: PA)

It is not known for certain how and when the print came to Oxburgh Hall, the home of the Bedingfeld family, who built the estate in 1482.

The print will be on show at Oxburgh alongside some 16th century textile fragments, preserved beneath the floorboards of the hall and conserved after being found during recent building work.