British athletes currently in isolation have been assured they won't miss Olympic competition if they continue to show negative tests.
Six members of the track and field team were initially confined to their rooms at Team GB's preparation camp in Yokohama.
All had been identified as a close contact of an individual, not part of the team, who tested positive on arrival in Tokyo.
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"Our testing protocols are extremely robust, not only to get into the country but also whilst we are here," said Team GB chef de mission Mark England.
"As a result of that and following our negotiations with the Japanese government and the health services in the Yokohama prefecture, nobody will miss their Olympic competitions. They are entirely allowed, under the rules of Tokyo 2020, to compete.
"They are confined to their rooms, which are single occupancy, and they have their meals there. In terms of their mental health and wellbeing they can also travel, separately, to training with their peers.
"Almost 800 members of Team GB are now in country and not one individual has tested positive for Covid. That's a great story and quite an achievement for us.
"Our athletes are all PCR tested, it's a more intensive than the saliva or lateral flow tests others are doing.
"We're as confident as we can be that we aren't bringing any variants in Japan."
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After winning 67 medals to finish second on the medal table in Rio, expectations are high, though sports data specialists Gracenote yesterday predicted 45 medals and 14 golds dropping Team GB down to fifth behind the USA, Russian Olympic Committee, China and hosts Japan.
"We don't look at predictions, we didn't in Rio and we didn't in London," added England.
"We just ask ourselves are we medal competitive and I believe we are.
"I don't know what the medal outcome will be, but this is a top team we're looking at. We know we can medal in every sport we're entered, it's very competitive."
England is confident Team GB - who have brought their largest ever squad to a foreign Games - is as best prepared as possible for the challenges of the days to come.
And it's not just worries about Covid, with temperatures in the mid-30s and 80 per cent humidity, this is predicted to be the hottest Games ever.
"We've done a lot of work on heat mitigation, from the kit we have to the cooling mechanisms we have for those competing outdoors," he said.
England also urged members of Team GB to ignore speculation about the Games, following a senior officials refusal yesterday to rule out cancelling the Olympics, should coronavirus infection rates rise.
"We have had absolutely no conversations on that Games being cancelled at all with anyone within the Olympic fraternity," he added, in an interview with Eurosport's Greg Rutherford.
"We had a Chef de Mission's meeting this morning and there was no conversational debate on that, but as I said competition started this morning and I'm very confident that competition will definitely be going ahead in 17/18 days' time and we'll reflect on a wonderful celebration of sport.
"There are a couple of things in there, as you know from your own experience you are in a mindset of performing now and any interruption to that can be distracting for sure, but you are pretty concentrated and determined on the task in hand."
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