A self-portrait has finally been verified as a Rembrandt following eight months of scientific analysis.
The 1635 painting, whose authenticity has been questioned for decades, depicts the Old Master looking out at the viewer while wearing a black cloak, a feathered bonnet and a metal band around his neck from a suit of armour.
Doubters included Rembrandt specialist Horst Gerson, who in 1968 said that areas of the painting were not accomplished enough to be the work of the famous Dutch painter.
He stated that the portrait was likely to have been painted by one of Rembrandt's pupils.
The National Trust, which owns the painting, was prompted to send the painting away for scientific analysis after another specialist, Professor Ernst van de Wetering, said he believed that the half-length portrait was genuine.
Experts at the Hamilton Kerr Institute (HKI) in Cambridgeshire have now removed several layers of aged and yellowed varnish and analysed the artist's signature.
Painting conservator Christine Slottvedd Kimbriel said: " What was revealed was a true depth of colour, much more detail and a three-dimensional appearance to the fabric in Rembrandt's cloak."
But she added: "It was close investigation of the artist's signature that gave us one of the biggest clues as to its true authenticity.
"The signature and date of 1635, inscribed both on the front and back of the panel, had been considered problematic in previous assessments as it was thought that the style and composition was much more akin to the artist's style slightly later in his career.
"But the cross-section analysis left no reason to doubt that the inscription was added at the time of execution of the painting."
Compositional changes - including the inclusion of Rembrandt's left hand in the original composition and alterations made to the shape of his hat - were revealed through i nfra-red reflectography and X-ray photography.
Ms Slottvedd Kimbriel said: "S uch alterations are present in many of Rembrandt's own works, suggesting a dynamic process of painting typical of Rembrandt."
Analysis of the cell structure of a thin cross-section of the wooden panel under the microscope showed that the wood was from the poplar/willow family, which Rembrandt used for some of his paintings.
Research showed that the pigments, including the blue mineral azurite and blue cobalt, were consistent with those used by Rembrandt and his studio assistants .
David Taylor, paintings and sculpture curator at the National Trust, said: " The varnish was so yellow that it was difficult to see how beautifully the portrait had been painted.
"Now you can really see all the flesh tones and other colours, as well as the way in which the paint has been handled - it's now much easier to appreciate it as a Rembrandt."
The portrait is dated 1635, when Rembrandt, who is considered to be one of the greatest painters in European art history, was 29 years old.
He was living in Amsterdam at the time and his self-portraits were becoming increasingly popular as his fame and wealth grew.
Rembrandt is thought to have depicted himself in at least 40 paintings b ut the National Trust painting, thought to be worth £30 million and featuring the artist in "fanciful costume", shows him continuing to feature role play in his portraiture and experimenting with painting different surfaces.
Prof Van de Wetering, the world's leading Rembrandt expert, said: "Although I was pretty certain the painting was a Rembrandt when I saw it in 2013, I wanted to further examine it after cleaning and see the results from the technical analysis as this had never been done before. With all this additional scientific evidence, I am satisfied it is by Rembrandt."
The painting was given to the National Trust by the estate of Lady Samuel of Wych Cross in 2010, when it was believed it was the work of one of Rembrandt's pupils.
Work on the portrait, which cost around £20,000, was funded by the People's Postcode Lottery .
The painting will go on display at Rembrandt Revealed, at Buckland Abbey in Devon, on June 13.