Portrait possibly of Jacob Jordaens, a friend and important contemporary of Rubens and Van Dyck.

The portrait - entitled Man with Beard - hangs high on the walls of the Green Drawing Room.

But Adam Busiakiewicz, the former head of historical interpretation at the castle, has just had an article published in the British Art Journal in which he suggests the portrait is not only an original work by Van Dyck but that he knows the sitter.

Adam began researching the provenance of the painting back in 2013, just as he left the castle to pursue his art studies.

He now works as a guide lecturer for the Wallace Collection in London.

Adam knows there are still many discoveries to be made on the walls of Warwick. But he knew that most of the castle’s world-famous collection of van Dycks and Rubens acquired during the 19th century had been sold off by the time he worked there.

The portrait of the mysterious man with a beard is only listed as “School of van Dyck” which is why Adam speculates that it might have escaped the attention of the great art sell-offs 40 years ago.

In his research published in the Art Journal he writes: “I believe the Man with the Beard is in fact the Flemish Old Master Jacob Jordaens, who was a friend and contemporary of van Dyck.

After comparing other 17th century portraits or Jordaens, Adam concludes: “It is my cautious suggestion that an exciting potential match has been established.

“Along with van Dyck and Rubens, Jacob Jordaens formed one part of the ‘holy trinity’ of artists - all three were commissioned to paint large alterpieces for the Augustian Church in Antwerp. All three were paid for their work - Jordaens is recorded to have received the same fee as van Dyck - and their professional lives would have brought then together.”

Warwick Castle’s general manager Geoff Spooner said: “Throughout the centuries, Warwick Castle has kept many secrets and some are still being unearthed due to our commitment to researching all our treasures.”

“For 200 years, this painting has been the subject of much interest among Warwick Castle residents and guests. Those in the know have remarked that the painting shows similarities with Van Dyck’s work, but until recently only ‘Man with Beard’ knew the secret of who he is and who painted him.”

“Through our painstaking programme of restoration and research, that secret is on the cusp of being revealed.”