The England pair are now having to isolate on the eve of Tuesday's game against the Czech Republic as a precaution following consultation with Public Health England, with discussions about the situation ongoing.

A PHE spokesperson told the PA news agency that it was "working with the FA to identify close contacts of Billy Gilmour and any risk to other players and staff", and indicated any decision to tell players from the England team to isolate was made by the Football Association.

Mount and Chilwell – like the rest of the squad – produced negative lateral-flow tests on Monday afternoon following negative results in Sunday's round of UEFA pre-match PCR tests.

Asked about their availability for the group decider, Southgate said: "Well, we don't know at the moment.

"There's obviously got to be quite a doubt, but there's still a lot of discussions and investigations going on behind the scenes, so at the moment they're isolating and we just have to find out over the last 12 hours or so."

Southgate, who had been due to have Mount alongside him at the pre-match press conference, added: "We had worked with the players this morning on the training pitch so then of course we find out when we finish that this is the situation.

"I can't say it isn't disruptive. We don't really know at this point whether they might be OK for (Tuesday) or they could be out for 10 days so there are a lot of unknowns frankly at this moment in time."

Among the many things Southgate is trying to get his head around is how England are having to prepare without two players whereas Scotland have avoided further absences despite Gilmour's positive test  being in their camp.

Steve Clarke's men have been under the PHE umbrella, having stayed in Darlington and used Middlesbrough's training ground – the same facilities used by England during their pre-Euros training base.

"I don't want to cause a drama for Scotland but if you're all in the dressing room together, where does everything stand? I don't know is the honest answer to that," he said.

"Our medical people are dealing with all of this. I've been updated as regularly as I can be which is every hour or so when there's a little bit more information and we have to accept whatever the situation is and adapt to it.

"That's the world we're all living in, across every family and every sport and every business."

Ex-England striker Gary Lineker shared similar confusion about the differing impact on the sides following news that Mount and Chilwell were isolating.

"This is odd," he wrote on Twitter. "They may have had close contact with Billy Gilmour, but If they continue to test negative surely they can play.

"Otherwise surely every single Scottish player, who all hugged Gilmour after the game, won't be allowed to play either. Makes no sense."

But Southgate – who expressed sympathy for Scotland counterpart Clarke following Gilmour's positive test – is not letting his attention waver, saying in tournaments "you have to adapt, you have to respond".

Asked why it just Mount and Chilwell, who were pictured embracing Gilmour on Friday, having to isolate, the England boss said: "I don't know all of the factors behind that.

"Clearly it's nothing to do with being on the pitch so that's why there is no issue with teams training, for example.

"Going to when the Premier League restarted training and matches were shown to be a situation where there weren't contacts for long enough for that to be a risk, so we're just waiting to hear more information at this moment in time.

"We know these things can appear four or five days down the line so that's what we've been living with all year in a football sense.

"Every time we are tested you are trying to do everything right across the camp.

"We have had nothing all year but we know a lot of that has been good practice, but some of that has been good fortune.

"And there's just so many touchpoints of interactions. Being in the bubbles as they've been has limited, but we are dealing with something that's very, very difficult to control entirely.

"But I think we've all accepted that and understood that for the entire season."