Three Old Master paintings of “very high value” were stolen from a University of Oxford gallery this week. The audacious heist follows a spate of smaller gallery thefts across the UK in the last few months, including the attempted burglary of Dulwich Picture Gallery in London.

‘A Soldier On Horseback’ by Antony Van Dyck (1599-1641) was painted around 1616 and is one of the priceless works stolen from Christ Church Picture Gallery. The acclaimed Flemish artist worked as a leading court painter in England under King Charles I and his works regularly sell for millions at auction. Annibale Carracci’s (1560-1609) ‘A Boy Drinking’ (c. 1580) and Salvator Rosa’s (1615-1673) ‘A Rocky Coast, With Soldiers Studying a Plan’ (c. 1650) are also missing.

London-based Old Masters dealer Philip Mould tweeted that this “is an unusual group to steal—neither priceless nor small fry.” Experts believe the three paintings could be worth up to £10.2 million.

It is unclear how the thieves were able to gain access to Christ Church on Saturday evening, although staff soon realised that several “important cultural artefacts” had been taken.

“The paintings which have been stolen are very high-value pieces dating back to the sixteenth and seventeenth centuries,” explained Detective Chief Inspector Jon Capps, from Thames Valley Police. “The artwork has not yet been recovered but a thorough investigation is under way to find it and bring those responsible to justice.”

Police are currently appealing for witnesses who saw or heard anything suspicious that evening to come forward, as well as for any footage from the area.

“It’s worth keeping in mind that it’s impossible to sell these paintings anywhere on the global open market,” remarked Mould. “The purpose of similar heists include: private theft to order, ransom objects (rarely effective); or collateral in underworld deals.”

Christ Church Picture Gallery is internationally renowned for its spectacular Old Master collection, which includes works by Leonardo da Vinci (1452-1519) and Raphael (1483-1520). Sir Richard Nosworthy bequeathed Rosa’s painting to the gallery in 1966. But Christ Church has cared for the other two artworks for over 250 years, after the bequest of college alumni General John Guise (1682/83-1765). Guise left more than 200 paintings and nearly 2,000 drawings to Christ Church in 1765.

The gallery will remain closed until further notice while the investigation is ongoing.