He said he had been wearing jeans for a lunch meeting, and “didn’t even think about” swapping them for a different pair of trousers when heading to the tournament.

He turned up wearing a shirt, blazer, dark jeans and dress shoes and played a few rounds before being asked to change.

When his offer to change for the next day was refused, Carlsen said it then “became a bit of a matter of principle for me.”

In a statement, FIDE confirmed the 34-year-old was fined $200 (£159), and said its rules were applied “impartially”. They cited a case where another player was fined on the same day before changing his shoes.

Carlsen is a five-time World Chess Champion, and retains the top ranking in the sport.

The Norwegian has long been considered a maverick in the chess world since becoming a grandmaster – the top title in chess – at the age of 13.

In a now-settled dispute with opponent Hans Niemann, Carlsen quit a tournament in 2022 after Niemann beat him, before going on to accuse his American rival of cheating.

Niemann had denied the allegations, and even said he would “strip fully naked” to prove his innocence.

The pair went on to settle a $100m (£79m) lawsuit in August last year.