Boris Johnson denied the NHS would be overwhelmed and said he was not prepared to lock down the country to save people in their 80s, texting his adviser “get Covid and live longer,” according to new WhatsApp messages released by Dominic Cummings.

In his first TV interview, the prime minister’s former chief adviser said Johnson held out on reimposing Covid restrictions because “the people who are dying are essentially all over 80.”

Cummings also told the BBC that Johnson had been determined to go to see the Queen in person, despite people in Number 10 already falling ill with Covid in March 2020. Downing Street denies the account.

In WhatsApp messages, shared with the BBC, that were sent to aides in mid October, Johnson appears to say: “I must say I have been slightly rocked by some of the data on Covid fatalities. The median age is 82 – 81 for men 85 for women. That is above life expectancy. So get Covid and live longer. Hardly anyone under 60 goes into hospital (4 per cent) and of those virtually all survive.

“And I no longer buy all this NHS overwhelmed stuff. Folks I think we may need to recalibrate.”

Dominic Cummings, during an interview with Laura Kuenssberg.

Johnson also appears to text aides “There are max 3 m in this country aged over 80” and says “it shows we don’t go for nationwide lockdown.”

The new messages will cast further doubt over the actions of the prime minister in the run-up to the November lockdown, a time during which Cummings and other senior scientists have said the prime minister was fiercely opposed to lockdowns.

Cummings told the BBC that Johnson, who came close to death after he was hospitalised with Covid in April 2020, told meetings in Number 10 that he should never have agreed to the first lockdown.

He said Johnson referred to the Telegraph as “my real boss” and was extremely concerned about the reaction of the right-wing press and the Conservative party.

“He then basically reverted and said, actually the whole thing was a disaster, we should never have done it, I was right in February, we should basically just ignore it and just let the thing wash through the country and not destroy the economy and move on,” he said.

Cummings said Johnson had repeatedly ignored the advice of his chief scientific and medical advisers.

“When you get to the week of around about 15 to 19 September, by that point the data was clear about what was happening and Patrick Vallance and Chris Whitty came to Downing Street and said erm, it’s clear where this is going, we think that you should consider hitting it hard and early … the prime minister said no, no, no, no, no, I’m not doing it.”

In the BBC interview, Cummings claims that he had to stop Boris Johnson going to see the Queen in person at the beginning of the Covid pandemic, when staff in Number 10 were already falling ill and the prime minister had already instructed the public to avoid all unnecessary contact, especially with elderly people.

“I said, what are you doing, and he said, I’m going to see the Queen and I said, what on earth are you talking about, of course you can’t go and see the Queen. He said, ah, that’s what I do every Wednesday, sod this, I’m gonna go and see her,” Cummings said.

Downing Street denied that this incident took place. Buckingham Palace declined to comment.

Cummings said he eventually convinced Johnson not to take the risk. “I said to him, there’s people in this office who are isolating, you might have coronavirus, I might have coronavirus, you can’t go and see the Queen. What if you go and see her and give the Queen coronavirus?

“You obviously can’t go … I just said if you, if you give her coronavirus and she dies what, what are you gonna, you can’t do that, you can’t risk that, that’s completely insane. And he said, he basically just hadn’t thought it through, he said, yeah, ‘holy shit, I can’t go.’”

A Number 10 spokesperson told the BBC: “Since the start of the pandemic, the prime minister has taken the necessary action to protect lives and livelihoods, guided by the best scientific advice.

“The government he leads has delivered the fastest vaccination rollout in Europe, saved millions of jobs through the furlough scheme and prevented the NHS from being overwhelmed through three national lockdowns. The government is entirely focused on emerging cautiously from the pandemic and building back better.”

Cummings has launched multiple attacks on his former boss after leaving Downing Street in December, including at a seven-hour committee meeting with MPs and through a new subscription blog.

The former chief adviser was subject to vociferous public criticism after the Guardian revealed he had travelled to Durham with his family, and later to Barnard Castle, during the national lockdown.

Cummings repeated his explanation that he had left London because of threats against his family – which he told MPs in May but declined to say at a press conference he gave about the incident. “Everything that I said in the Rose Garden was true … but I didn’t go into all of the security concerns in the background,” he said.

“The way we handled the whole thing was, was wrong on the Monday. What I should have done is either just resigned and said nothing about anything, or I should have spoken to my family and said, listen we’re just gonna have to come clean about the whole thing.”