Police have confirmed they attended a property in County Durham after it emerged that Dominic Cummings travelled more than 260-miles from his London home during the lockdown that his boss had just announced.
Political leaders have piled pressure on Mr Johnson to sack the 48-year-old strategist for flouting the rules.
The matter is bound to irritate the public – praised by ministers and officials for its high compliance with the restrictions since they were brought in on March 23 – which faces another bank holiday weekend apart from family members.
Downing Street has so far refused to comment.
The news comes as authorities managing beaches and beauty spots are bracing for a big influx of visitors expected to put social distancing rules under strain.
Following the easing of some lockdown measures last week, there are no restrictions on how far people can go to get to the countryside, National Parks and beaches in England.
But the authorities in many tourist hot spots are urging people to stay away.
Questions also remain over whether Britons will be able to go on holiday this summer after Home Secretary Priti Patel announced plans, due to come into force on June 8, for travellers – including residents returning home from breaks – to quarantine for two weeks on their arrival into the UK.
Ms Patel, speaking at the Downing Street briefing on Friday, said the Government guidance continues to be that all but essential travel abroad was advised against.
The details of Mr Cummings’s Durham visit only added to scrutiny of No 10.
According to a joint investigation by the Daily Mirror and the Guardian, at the same time as the UK Government was instructing people to remain home – with fines in place for those contravening the rules – Mr Cummings decided to escape the capital.
He is said to have been present at his family home when police from Durham Constabulary turned up on March 31, following a call from someone reporting they had seen Mr Cummings in the area.
Durham Police confirmed officers had spoken to the owners of an address after reports a person had travelled there from London.
A spokesman said: “On Tuesday, March 31, our officers were made aware of reports that an individual had travelled from London to Durham and was present at an address in the city.
“Officers made contact with the owners of that address who confirmed that the individual in question was present and was self-isolating in part of the house.
“In line with national policing guidance, officers explained to the family the arrangements around self-isolation guidelines and reiterated the appropriate advice around essential travel.”
An unnamed neighbour told the two papers Mr Cummings was seen in the garden five days after the police visit as Abba’s Dancing Queen was playing loudly.
“I got the shock of my life, as I looked over to the gates and saw him,” they said.
“I recognised Dominic Cummings, he’s a very distinctive figure.”
Former Conservative MP David Lidington, who was de facto deputy PM under Theresa May, was among those saying the news raised serious questions.
He told BBC Newsnight: “There’s clearly serious questions that No 10 are going to have to address not least because the readiness of members of the public to follow government guidance more generally is going to be affected by this sort of story.”
Similar examples of public officials ignore lockdown guidelines have led to resignations and condemnation from senior Tories.
When Professor Neil Ferguson, the epidemiologist whose modelling prompted the lockdown, quit as a member of the Scientific Advisory Group for Emergencies for flouting distancing rules when he was visited by his girlfriend, Health Secretary Matt Hancock said he was “speechless”.
Downing Street had previously confirmed Mr Cummings had started displaying coronavirus symptoms “over the weekend” of March 28 and 29.
The same day as police spoke with members of Mr Cummings’s family, his boss Mr Johnson was admitted to hospital with coronavirus, where he would later require treatment in intensive care.
SNP Westminster leader Ian Blackford MP said the aide’s position was “completely untenable”.
“He must resign or be sacked,” he added.
Sir Ed Davey, acting leader of the Liberal Democrats, called for Mr Cummings to quit over the allegations, while a spokesman for Labour said: “The British people do not expect there to be one rule for them and another rule for Dominic Cummings.”
But friends of Mr Cummings suggested he would be going nowhere.
One told the PA news agency: “He isn’t remotely bothered by this story, it’s more fake news from the Guardian.
“There is zero chance of him resigning.”
In other news:
– Children could be half as likely to catch coronavirus as adults, according to a review of global studies led by University College London.
– The Government’s Scientific Advisory Group for Emergencies (Sage) published papers assessing the impact of relaxing school closures on June 1, stating that the evidence on how likely children are to transmit Covid-19 remains “inconclusive”.
– The so-called R-number, the average number of people that will contract coronavirus from an infected person, was between 0.7 and 1.0 across the UK two to three weeks ago – slightly higher than the last rate declared by ministers.
– The number of deaths involving Covid-19 in the UK passed 45,000, according to the latest available data.
On top of pressure over Mr Cummings, ministers were facing backlash from the aviation and travel sector following the publication of more details of plans to subject international travellers to spot checks and £1,000 fines if they fail to self-isolate for 14 days after arriving in the UK.
Exemptions for road hauliers, seasonal agricultural workers and medical officials will apply, while the common travel area with Ireland will be unaffected.
But arrivals from France will not be exempt, following confusion in recent days.
Virgin Atlantic warned the plan would keep planes grounded.