The tennis players had only attended one session at the facility when they mutually agreed to go for one last feast before committing to the programme.

Venus laughed to Harper’s Bazaar UK: "We went to the opening lecture, looked at each other and decided we should go out to a restaurant.

"We had steak and chocolate cake – I don’t even eat dessert! We were staying for three weeks, so we knew this was it!"

Although the sisters played doubles together for years and have come face-to-face in singles matches, Venus insisted they rarely ever talked about their sport.

She said: "We just gossip. We’ve both been on a very stringent eating programme recently, so we’re supporting each other with that."

The 44-year-old sportswoman loves spending time with her younger sister’s two daughters, Olympia, seven, and 12-month-old Adira.

Venus gushed: "It’s wonderful. You don’t have to be the one doing the disciplining. You get to come for the fun parts.

“Although, as soon as I go over there the older one wants me to start running around. Who wants to do that! I’m so tired of running. Can’t we sit and play Lego or something?"