It is hardly the most flattering of likenesses, but a pencil sketch of a woman's head has been identified as a rare self-portrait by Charlotte Brontë. It dates from 1843, four years before she was to publish Jane Eyre, one of English literature's great masterpieces, and when she was suffering the acute agony of unrequited love. The discovery has been made by the acclaimed literary biographer, Claire Harman, who describes it as 'massively significant' as there are only two other known lifetime portraits.