It’s said to be the “only reasonably certain portrait from life” – a sketch by Jane’s older sister Cassandra which purportedly depicts the artist.

Found on display in Room 18 of the National Portrait Gallery, the pencil and watercolour sketch dates from about 1810 and was purchased by the gallery in 1948 for £135.

The image was the basis for a late 19th century water-colour image of Jane which was created by Maidenhead artist James Andrews who traced Cassandra’s sketch.

Andrew’s image had been commissioned by Jane’s nephew, James Edward Austen-Leigh, and he used an engraving of it – made by William Home Lizars – as a frontispiece to his biography, A Memoir of Jane Austen.

It is an image of that engraving which features on the new £10 polymer banknote going into circulation tomorrow.

The decision to use the later image rather than the original has attracted some criticism – not for the subject but for the fact that, as historian Lucy Worsley told The Sunday Times, it represents “an author publicity portrait after she died in which she’s been given the Georgian equivalent of an airbrushing”.

There has, we should also note, been some criticism of the choice of quote on the note – “I declare after all there is no enjoyment like reading” comes from Pride and Prejudice and was uttered by the deceitful Caroline Bingley who really has no interest in reading at all!

WHERE: Room 18, National Portrait Gallery, St Martin’s Place (nearest Tube station is Charing Cross or Leicester Square); WHEN: 10am to 6pm daily; COST: Free (donations welcome); WEBSITE: www.npg.org.uk

PICTURE: Jane Austen by Cassandra Austen (pencil and watercolour, circa 1810 – NPG 3630) © National Portrait Gallery, London