Serena was fined £50,000 and given a suspended ban from Flushing Meadows over the next three years for the threats she directed at a line judge who foot-faulted her during her semi-final against Kim Clijsters.

While an immediate suspension was never likely to materialise, the fine, which could double if Williams commits another major misdemeanour at a grand slam event, was lower than had been widely expected.

Seeing the funny side: Serena and her friend share a laugh after her slip-up

Williams earnings from the singles and doubles events at the tournament were £334,307, so the penalty was covered by what she made from that fortnight alone.

The possible £106,658 that she could forfeit is, in effect, a match fee fine, as that is the difference between the money paid to singles quarter-finalists and beaten semi-finalists.

Williams was within two points of losing when she went berserk at the female line judge and threatened, among a blitz of colourful language, to ram the ball down her throat.

Outburst: Serena Williams (right) confronts the line judge at the US Open

While the threat of a future suspension sounds severe, she would need to commit another major offence at a grand slam for it to kick in. Were she to receive a code violation at another grand slam for smashing her racket, for example, that alone would not trigger the ban.

Australian Lleyton Hewitt was fined £60,970 (reduced to £12,199 on appeal) in 2002 by the ATP Tour for refusing to fulfil media commitments.

The previous biggest punishment meted out was to the American Jeff Tarango, who walked off the court at Wimbledon and accused officials of being corrupt. He was barred from Wimbledon the following year and fined £29,274 for his outburst.