“Problem with Prince’s Regimental tie knot is unravelled.”

A portrait of the Prince of Wales was unveiled for the second time yesterday after the artist had to change the way his regimental tie was painted.

The painting shows Prince Charles wearing the Gordon Highlanders' tie but the original version showed it knotted with a yellow stripe, which goes against the regiment's tradition. He was not wearing the tie while sitting for the portrait and it was just before its first unveiling at the regiment's museum in Aberdeen in the presence of the Prince that the artist was told of his mistake.

Richard Stone, who has painted every member of the entire Royal family, said: "You could call it a knotty problem. The sittings lasted about an hour and because Prince Charles had to rush off for other engagements there was not the time for him to change clothes.

"A member of his staff gave me the tie and I thought it looked rather good with the yellow in the middle. The mistake was embarrassing at first. It only took a minute or so to fill in the yellow with black but I had to wait until I could return to Aberdeen to unveil it again."

Mr Stone, of Colchester, has provided the painting free to the independent museum and 350 limited edition prints are also being sold to raise money for the museum's upkeep.

It is unclear how the tradition of knotting the Gordon Highlanders' tie started. The regiment was formed in 1794 to deal with the French revolutionary wars and Prince Charles was its last Colonel-in-Chief before it was joined with the Queen's Own Highlanders six years ago.

The Prince of Wales visited the Strathisla distillery in Keith, yesterday - the home of Chivas Regal - and examined their whisky but resisted the temptation to taste it.