They are on a fourth-round collision course and have withdrawn from the women’s doubles to dedicate their efforts to their singles campaigns.

Venus Williams, 35, has faced questions about retirement for many years, and the five-time Wimbledon champion said of her career: “It’s a great job. It’s fun out here.

“You can only do it for a little while in comparison to how long you won’t be doing it. So that’s my whole thing.”

Assessing the searing midweek sun threat, she added: “We’ll see how it affects the conditions of the courts.”

The women’s tour has a rule that can allow players a 10-minute break between the second and third sets, if their match begins in conditions above 30 degrees Celsius.

While in some quarters debate has been stirred up because the men’s and women’s tours have differing heat policies – the men’s rule is simple: play through it - the players at Wimbledon have expressed no great concern.

Some have even gently pointed out that peak London heat does not come close to some of the conditions they encounter on the globetrotting tour.

Venus Williams plays Yulia Putintseva on Kazakhstan today while Serena takes on Hungarian Timea Babos. Both will be aiming to avoid joining the seeded casualties after last year’s runner-up Eugenie Bouchard and third seed Simona Halep were bounced out on Tuesday.