The British and Irish Lions will proceed with their summer tour to South Africa after all alternative contingency plans were ruled out.
However, a number of obstacles still need to be overcome, with Lions board member Bill Sweeney confirming cancellation would be the only option left if it is unable to go ahead for any reason.
A joint statement outlined the decision to stage the event in South Africa, although it is understood that a reduced number of games and destination cities compared to the original eight-match itinerary is likely.
Sweeney revealed that time has effectively run out on organising a 'home' tour in the UK and that postponing it to 2022 was unfeasible. An offer from Rugby Australia had already been rejected.
Whether spectators will be present for games is yet to be known amid expectations in South Africa of a third wave of coronavirus surfacing in June.
"It was always the preference to be able to honour and go ahead with the tour in South Africa," Rugby Football Union chief executive Sweeney said.
"You would always want it to be with crowds rather than behind closed doors because that would be a different environment.
"But things change quickly. Who knows? Is it possible that we will get crowds there?
"We're running out of time for a UK option, frankly. The days are ticking by. it could have been a very, very good fallback option.
"One of the hardest things in life, not just in rugby, is changing the rugby calendar. It was just felt that the postponement option was extremely difficult to pull off."
While there is now clarity around what form the Lions tour will take, SA Rugby boss Mark Alexander hinted at the challenges ahead, with the joint statement stopping short of guaranteeing the event will proceed.
"We have been in regular contact with our government to make that a reality against the backdrop of the pandemic and its predicted progression over the coming months," Alexander said.
"There are serious financial implications for SA Rugby should the event take place without any supporters in attendance, and we cannot ignore that in our considerations.
"But we are determined that the eventual outcome will deliver the best occasion and experience for players, supporters and our commercial partners."
Lions chairman Jason Leonard added that "we acknowledge there is a significant amount of work still to be undertaken to deliver a robust Covid-19 countermeasure plan to ensure a successful, safe and uninterrupted tour".
To underline Leonard's point, England's cricket team abandoned their tour of South Africa in December following a number of positive tests for coronavirus despite operating in a bubble environment.
"We have seen already in cricket when they went to South Africa and players halfway in said they did not feel comfortable with the protocols in place and the welfare issues in place. The side returned home," Sweeney said.
"We have to work with South Africa and make sure they have got the right environments there.
"We have to make sure the players' health and welfare is absolutely of a level we can accept."