Curators of an exhibition by John Constable have made fresh discoveries about two portraits now believed to be the artist's parents Ann and her husband Golding.

The portraits, now thought to make a pair, have been in the collection at Colchester and Ipswich Museum service since 1926

Anne Lyles, Tate curator and authority on the work of Constable, and writer and critic Martin Gayford, have confirmed that a portrait of Ann Constable, Constable's mother, is by the artist.

They have also provisionally re-identified a portrait of Constable's father, Golding Constable that was previously thought to depict his schoolmaster.

The portraits, now thought to make a pair, have been in the collection at Colchester and Ipswich Museum service since 1926.

The discoveries were made while conducting research for an exhibition at the National Portrait Gallery, which will include the portrait of Golding Constable.

Painted around 1805, the recently authenticated portrait of Constable's mother sees the sitter pictured facing left with a spaniel in her lap.

The portrait was painted on canvas supplied by T Brown of Holborn, an artist's merchant known to have been used by Constable.

The recent authentication of the picture has thrown light on the likely identity of the sitter shown in the male portrait, who was previously identified as Constable's schoolmaster, Dr Thomas Lechmere Grimwood based on its description in a 1926 Sotheby's sale catalogue as a "Portrait of the artist's schoolmaster".

The sitter is said by exhibition organisers to have a strong resemblance, with the same jowls and brown curled wig as a later portrait of Golding Constable, circa 1815, which belongs to Tate.

The book held by the male sitter is also said to closely resemble the Constable family Bible, which is still in existence.

Both portraits have shared the same provenance for many years, descending through the same branch of the Constable family.

They face complementary directions which suggest they are intended as a pair.

Constable Portraits: The Painter and His Circle, which carries a £5 admission charge with concessions available, will take place at the National Portrait Gallery from Thursday until June 14.

The portrait of Ann Constable is on display in the Wolsey Art Gallery in Christchurch Mansion, Ipswich.