George Hunter of Edinburgh and London was commissioned to make full Highland regalia for the not inconsiderable sum of £1,384.18. The effect was so striking that the King was painted wearing it by Sir David Wilkie a few years later. Now the tartan doublet has been rediscovered in a trunk in a castle in Germany and its history traced.
It is expected to fetch up to €15,000 (£10,000) in what will be one of the largest auctions ever held when the Royal House of Hanover, a German royal family, puts 20,000 pieces on the market next week.
The House of Hanover is headed by Prince Ernst, husband of Princess Caroline of Monaco, but much of the property descends from five British kings - Georges I to IV and William IV, who were also electors of Hanover - making it the biggest sale of items of British royal provenance. The auction is being held at the family's summer palace, Schloss Marienburg, over 10 days from Wednesday.
Kerry Taylor, a Sotheby's expert, pinned down the significance of the waistcoat only yesterday when she found the Wilkie painting in the records of the British Royal Family's art collection.
She said: "I had a feeling it could have belonged to King George IV but had no proof. ... The final piece of the jigsaw was while thumbing through a catalogue of works in the Royal Collection, I saw the picture by Wilkie in which the king is depicted resplendent in the doublet. There was no doubting it was the self-same piece that was in the Hanover sale."
The spectacular arrival of the King at Holyrood Palace on 17 August 1822 in his tartan regalia is said to have caused a sensation.Sir Walter Scott, who had done much to revive interest in Scotland and its Romantic past, convinced the king that he was not only a Stuart prince but also a Jacobite Highlander and could justifiably wear such an outfit.
David Stewart of Garth, one of the founders of the Celtic Society, helped to devise the king's dress which was Scottish with a twist. The rich, soft velvet and gold embroidery would not have been normal but would have made the hard woollen tartan more comfortable.
Sir David Wilkie painted the king wearing his fabulous ensemble in 1829. The painting remains in the Royal Collection along with accessories including the sword, waist-belt and powder horn which the king is also seen wearing.