A painting by a British 18th Century artist has been saved for the nation.
Joseph Wright's Self-Portrait at the Age of About Forty has been unveiled at Derby Museum and Art Gallery, which holds several of his other works.
The painting was accepted in lieu of inheritance tax by the Government and allocated to Derby.
The National Heritage Memorial Fund donated almost £2.3 million towards the acquisition, alongside the Art Fund and a number of private donations.
The deal was administered by Arts Council England, with Arts Minister Lord Parkinson said it was wonderful the work had been saved.
Known as Joseph Wright of Derby, the painter is famous for capturing scenes from the burgeoning world of science.
The painting was accepted in lieu of inheritance tax by the Government and allocated to Derby in a deal administered by Arts Council England.
Experts said the self-portrait captures a sense of the painter's self-confidence, amid Wright's growing reputation for his so-called "candlelight paintings".
It is also the only one of Wright's ten self-portraits in which he specifically depicts himself as an artist.
The painting also comes with an added bonus, with its reverse showing a study for one of Wright's most famous works An Experiment on a Bird in the Air Pump, which is now on display in the National Gallery.
Owned as part of a private collection since it was completed in around 1772, the self-portrait has seldom been exhibited in public.
The painting, which is approximately 30 by 25 inches (76 x 63cm), is in its original elaborate frame and will be on permanent display in a bespoke free-standing case which will allow both sides of the painting to be viewed.
Lucy Bamford, curator at the museum and a Joseph Wright expert, said: "We are extremely excited to be able to add this remarkable painting to our existing Joseph Wright collection.
"The way it depicts his growing confidence as an artist is wonderful.
"We are delighted to have it on permanent public display where it can be enjoyed by local, national, and international followers of Wright's work."
Tony Butler, director of Derby Museums said: "The acquisition of this painting is a triumph for Derby Museums.
"The work has never been in public ownership, having remained in private hands since it was executed in a studio not far from where Derby Museum and Art gallery is now."
Lord Parkinson said: "It is wonderful that this rare self-portrait by Joseph Wright has been saved for the nation and acquired by Derby Museums.
"Thanks to the Government's Acceptance in Lieu scheme, this fantastic piece will be exhibited at Derby Museum and Art Gallery where it will take pride of place in the world's largest collection of his works."