Serena Williams has complained of excessive dope-testing demands after a tester working for Usada visited her in Florida outside her specified “whereabouts" window and found her not at home.

When informed of the visit, Williams then phoned the head of the Women’s Tennis Association, Steve Simon, to say that she was being unfairly targeted. Simon told her that this was a Usada issue, and that he would pass her views onto Travis Tygart, the organisation’s head.

But the story escaped into the public domain after Simon was overheard discussing the case on his mobile phone in a public area of San Francisco Airport. An eavesdropper forwarded the information to the Deadspin website, which published it late on Wednesday night, UK time.

It should be emphasised that no athlete is obliged to comply with a testing visit if it is not made during the 60-minute window for which the athlete identifies their whereabouts in advance each day.

The Deadspin report also highlighted the fact that Williams appears to have been tested a disproportionate amount of times in 2018, having already given five samples to Usada before this latest visit – which occurred at 8.30am on June 14 – while most other American tennis players had been tested only once or not at all.