Another 'Brontë' auction

After selling two doubtful portraits of Emily Brontë (one and two), auctioneers JP Humbert are now selling this portrait of the 'Brontë sisters' (for a full discussion of the pros and cons of it actually showing the Brontës we suggest you grab something to eat/drink and read the comments of this post). The upcoming auction is reported by several news outlets, such as the Telegraph:

An auctioneer is hoping to score a hat-trick, selling a third item believed to be linked to the literary Bronte sisters.
The painting, thought to be a hitherto unknown watercolour of all three sisters, is the latest in the series of unrelated items concerning the trio to go under the hammer.
Believed to be painted by 19th century English artist Sir Edwin Landseer, it will be included in a two-day fine art and antiques sale later this month at J.P.Humbert Auctioneers in Northamptonshire. [...]
Auctioneer Jonathan Humbert said there was no estimate on the latest discovery as it was impossible to say how much it would fetch, but he was hoping for a third sale of a Bronte-related artefact.
Mr Humbert said the painting, which appears to show all three sisters, has been attributed by a team from the National Portrait Gallery as well as four years of research by the vendor.
He said there were 10 evidential reasons supporting the suggestion it is of the Bronte sisters, and said its quality suggested it could only be attributed to an artist of Landseer's distinction.
The piece of art is believed to be signed by Landseer, and matches known features of the sisters.
"This is an exciting and important painting of museum quality and has a story to tell," he said. "I hope the art world will embrace it accordingly.
"There really is every possibility this is by Landseer and of the three Bronte sisters." [...]
The latest painting relating to the sisters is set to go under the hammer on April 26 as part of a two-day fine art and antiques sale at J.P.Humbert's saleroom in Towcester, Northants. Bronte blog