EDITOR'S NOTE: An earlier version of this story reported that 0.5% of people flying into the UK had coronavirus, based on Professor John Ashton's evidence to MPs. He later clarified that the 0.5% figure referred to the estimate for imported cases at March 23, not that 0.5% of all people arriving in the UK have coronavirus.
A tiny number of coronavirus sufferers were allowed to fly into the UK during April, according to the chief scientific adviser to the Home Office.
So far arrivals to the UK have not been tested for the virus - nor required to go into quarantine.
But that is set to change under the Prime Minister's plans for easing lockdown.
In his address to the nation on Sunday evening, Boris Johnson announced that arrivals by air would be required to self-isolate.
Professor John Aston told the Commons' Science and Technology Committee that 95,000 people arrived in the UK by plane between April 1 and 26, including 53,000 UK citizens.
Asked if there is an estimate of how many of those had Covid-19, he replied: "We believe that less than 0.5% of those people arriving potentially had Covid-19."
But later in the same hearing, he tried to clarify the figure, saying that 0.5% of total cases in the UK were estimated to be imported - not that 0.5% of all arrivals were sufferers.
He went on to say that "less than 0.5% of those arriving were due to the total cases of Covid-19 in the UK".
Prof Aston told the committee that the Scientific Advisory Group for Emergencies (Sage) used "complicated modelling" to calculate the estimate.
"It requires you to understand the prevalence (of Covid-19) within overseas countries as well as the prevalence within the UK," he said.
The Covid-19 “road map” published on Monday appears to contradict Boris Johnson's assertion that it would apply only to “people coming into this country by air”.
The document says: “The government will require all international arrivals not on a short list of exemptions to self-isolate in their accommodation for 14 days on arrival into the UK.
It adds that anyone without a pre-arranged place to stay “will be required to do so in accommodation arranged by the government.”
The government said the measures “will be introduced as soon as possible”.
Travellers from the Republic of Ireland, as well as the Isle of Man and the Channel Islands, will be exempt.
* This story was corrected after publication to reflect an error in the calculation of percentage. Half a percent of 95,000 people is 475 people not 4750.
