His pictures are seen as the embodiment of rural English cosiness, but John Constable's paintings belie a forbidden private passion. He first met Maria Bicknell when he was 24 and she was just 12. Years of family disapproval and on-off courtship ensued before they finally married, but Maria died at just 40. Andrew Graham-Dixon argues that it was this devotion to his love that proved the catalyst for Constable to revolutionise landscape art.

(Postponed from 22 March)