Hidden in an envelope for decades, a new Old Master

The elderly gentleman clearly hoped he owned something of note when he presented his envelope to the art experts. When they took a peek inside, they were staggered by what they found - a completely unknown painting by the Old Master El Greco.

The elderly gentleman clearly hoped he owned something of note when he presented his envelope to the art experts. When they took a peek inside, they were staggered by what they found - a completely unknown painting by the Old Master El Greco.

The small panel had been in the family of the old man in Spain for generations but is now to be sold in a sale in London in December where, despite measuring less than 24cm by 18cm, it is estimated to make up to £600,000.

Paul Raison, the head of Old Master pictures at Christie's, London, who discovered the work in Aragon in Spain with his Spanish equivalent, Pablo Melendo, said it was a wonderful find that was completely unexpected.

"This is a wonderful, vibrant work that has an impact that goes well beyond its modest dimensions," he said.

The painting, The Baptism of Christ , stems from the early part of the career of Domenikos Theotokopoulos, commonly known as El Greco because he came from Crete.

He travelled through Italy and then on to Spain as he developed the style for which he became famous and which was seen by thousands at the recent exhibition at the National Gallery in London.

But when this work was painted in the 1560s, El Greco, who had been a Byzantine icon painter, had just discovered the art of Venice, and notably of Titian. Surviving paintings from this period in his career are extremely rare.

The man who owned the small, devotional panel lived in "fairly modest surroundings". He handed over the envelope that he kept it in, clearly hopeful it was of significance as it had been handed down to him through his family.

As soon as Mr Raison saw it, he was "pretty confident" it was by El Greco, though it was taken to Madrid for further tests. It turned out to be related to an altar piece, the Modena Triptych, dating from 1568 in the Galleria Estense in Modena, that features a similar scene.

The painting will be sold in London on 8 December. Also in the sale is another work which is even rarer than the El Greco - one of only six identified still lifes by the Spanish painter Juan Sanchez Cotan. He painted fairly undistinguished figurative works but is regarded as a master of still life.