And England have since confirmed that illness had kept Stones from participating in their second training session after arriving in Germany. But fears have arisen that the bug could spread among the camp, with the national team desperate to avoid the squad being infected further.

Sky Sports claim that Stones is being confined to his bedroom to prevent the possibility of a spread and it remains to be seen when the centre-back will be able to rejoin the group.

He was part of a fully fit squad on Tuesday after being taken off with an ankle knock in the friendly defeat to Iceland, though Southgate insisted that the substitution was only precautionary.

"We think he's probably OK but we didn't want to take a chance given what's coming up,” Southgate explained. "[It was] mainly precautionary, he obviously took a bit of a knock to the ankle very early in the game. At half-time there was no point in taking any chance. We're too close to the start of the tournament and there was no point risking it."

With Harry Maguire unavailable this summer due to injury, Southgate may be without both of his senior centre-back options for England’s Group C opener in Gelsenkirchen, as the likes of Marc Guehi, Joe Gomez, Ezri Konsa and Lewis Dunk wait in reserve.

Having made just one league start in the past three months for City, Stones would have been looking to build up his fitness throughout the tournament, starting with the physical challenge of keeping ex-Fulham talisman Aleksandar Mitrovic at bay.

Should he miss out, Stones faces an uphill battle and will next target the June 20 clash with Denmark, when he would be likely to partner Guehi if fit.

But England’s current priority is to avoid the further spread of illness, after Southgate saw fitness doubts Bukayo Saka and Luke Shaw return to training, hoping to have every member of his 26-man squad available to produce a deep run into the tournament.