David Cameron played down the prospect of a national unity government to respond to the Covid-19 crisis, as he sent his best wishes to Boris Johnson.

The former Conservative prime minister said people can be reassured by the “incredible machine” of the civil service which will prepare decisions for the Prime Minister or for his deputy Dominic Raab.

He added it is right that opposition parties are included in briefings and have decisions explained to them, adding: “I don’t think that needs to change.”

Asked about the prospect of former prime ministers getting involved in such a national government, Mr Cameron told BBC Radio 4’s World At One: “I’ve been pretty quiet because I think the best thing an ex-prime minister can do is let the current Prime Minister get on with the important job they’re doing.”

Mr Cameron earlier said the Government has a “very clear strategy” in responding to Covid-19.

Asked who is in control of national security, Mr Cameron reiterated how any decision on any issue would go through Cabinet committees, Cobra and then be signed off by Mr Raab if the PM cannot take it.

Mr Cameron, who has been friends with Mr Johnson for decades, began by wishing the PM well.

And in a separate interview with ITV News, Mr Cameron said: “It’s very worrying news and all of us are praying for Boris and thinking of him and praying and thinking of his family.

“And hoping he gets well soon and gets back to Number 10, where I know he wants to be and where we all want him to be.

“Boris is very tough, very resilient, very fit person, I know that from facing him on the tennis court and I’m sure he’ll come through this.

“Of course he’s very resilient, he’s tough, also he’s got a tremendous zest for life, and getting things done, and for leading and for taking decisions.

“I know he’ll want to get well and get back in charge again, and that’s what we all want for him.

“And we’re hoping and praying that that’s the case and that’s the case very soon.”