English Heritage has appealed for information about the missing portraits from Leighton’s original series, one of which is known to have been sold at auction 25 years ago.
They depict the 7th Earl Cowper – Francis Thomas de Grey Cowper, Lady Adine Eliza Anne Cowper – and Lady Amabel Frederica Henrietta Cowper.
The other two family portraits in the set have already been returned to Wrest Park, on loan from a private collection, after more than 100 years.
They depict Hon Henry Frederick Cowper and Lady Florence Amabel Cowper.
The newly returned paintings have been loaned to English Heritage by descendants of Nan Cooper (née Herbert), who was the daughter of Lady Florence.
Cooper transformed the manor house into a hospital during World War One, and became its patron in 1915, before selling it the following year – bringing an end to her family’s long association with Wrest.
