His image in curled wig, embroidered red tunic and lace ruff stares out from kitsch portraits, decorative porcelain and chocolate boxes without number, but nobody really knew what Wolfgang Amadeus Mozart looked like – until now.

To the great excitement of musical scholars, two previously-unknown oil portraits painted from life– and which can be traced back to a close friend of the composer’s father – have been discovered.

They were identified by Cliff Eisen, Professor of music history at King’s College London, who has found documentary evidence that links them to letters written by Mozart and his father, Leopold.

One was painted in 1783, during the composer’s early years in Vienna when he was in buoyant mood after his marriage to Constanze. Measuring about 19in by 14in (47x35cm), it is by Joseph Hickel, painter to the imperial court. It is now considered so important that it has been insured for £2 million.

The second shows the child prodigy composer with his sister Nannerl, around 1764, when he was about eight.

Professor Eisen has linked the distinctive red coat with mother-of-pearl worn by the subject of the 1783 portrait to a letter that Mozart sent to one of his patrons, Baroness Martha Elisabeth von Waldstätten, in 1782.

“As for the beautiful red coat that tickles my fancy so dreadfully, I’d be grateful if you could let me know where I can get it and how much it costs, as I’ve forgotten. I was so taken by its beauty that I didn’t notice the price,” he wrote. “I really must have a coat like that, as it’s worth it just for the buttons that I’ve been hankering after for some time. . . They’re mother-of-pearl with some white stones round the edge and a beautiful yellow stone in the centre.”

Shortly afterwards, he wrote again “to thank your Grace for having immediately taken so much trouble over the beautiful coat.”

The other portrait shows Mozart with his sister wearing elegant English clothes that their father mentioned in letters, noting how fine his children looked in them. Leopold picked up such outfits on their tour of London in the 1760s, when the boy Mozart wowed audiences including George III and Queen Charlotte.

Both paintings, which will be revealed at a London conference this weekend, were acquired by an American collector from descendants of Johann Lorenz Hagenauer, Leopold’s close friend, banker and landlord. The two families had children of similar ages and diaries record repeated visits.

Professor Eisen said: “Considering their professional and personal relations, it is only to be expected, perhaps, that some items once owned by the Mozarts, or items that passed through their hands, might have ended up with the Hagenauers.”

The romanticised image of Mozart used on the wrappers of the chocolate balls that bear his name was painted 18 years after his death – by someone who had not seen him for 36 years.

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