A work by 17th century master Anthony Van Dyck is among three "very high value" paintings stolen from a University of Oxford art gallery.
A Soldier On Horseback by the Flemish artist, a leading court painter in England under King Charles I, dates from around 1616.
Two other works were stolen from Christ Church Picture Gallery, St Aldates, at about 23:00 GMT on Saturday.
Police said a thorough investigation was under way to recover the paintings, and the gallery will be closed until further notice.