Another top Government coronavirus expert had to remotely give a national update on the pandemic on Friday as they were self-isolating.

Deputy chief medical officer Professor Jonathan Van-Tam said he was appearing remotely at Friday’s Downing Street press conference as he was self-isolating due to a “household contact”.

He is the latest high-level official to go into self-isolation as Prime Minister Boris Johnson, NHS national medical director professor Stephen Powis, and Baroness Dido Harding, who leads the NHS Test and Trace programme, have also had to take the same action.

Mr Johnson answered Wednesday’s Prime Minister’s Questions virtually from Downing Street.

Mr Johnson, who has tested negative for coronavirus, appeared on television screens in the House of Commons chamber after being confined to Downing Street.

It came after he had contact with Tory MP Lee Anderson who tested positive for coronavirus.

Since both Prof Van-Tam and Prof Powis were self-isolating, only Health Secretary Matt Hancock appeared live at Friday’s Downing Street conference.

Prof Powis told a Downing Street briefing on Wednesday that he was self-isolating after a member of his household tested positive for coronavirus.

He said: “I am on Zoom today. I can’t join you in Downing Street and that’s because a member of my household recently tested positive for Covid and on the instructions from Test and Trace I am self-isolating.

“I should say I am completely asymptomatic and perfectly fine but I will be staying at home until I have completed my period of isolation.”

Just a few hours earlier Baroness Harding said she was self-isolating after receiving an alert from the service she runs.

The Tory peer tweeted a screenshot of an app notification that said “you need to self-isolate” until 11.59pm on November 26.

Baroness Harding, the interim executive chair of the National Institute for Health Protection, wrote above the image: “Nothing like personal experience of your own products …. got this overnight. Feeling well. Many hours of Zoom ahead.”

Someone told to self-isolate by the NHS Covid-19 app must do so for 14 days from the day they were last in contact with a person who tested positive for coronavirus, as it can take up to 14 days for symptoms to appear.

An alert from the app is received once that close contact has booked a test, taken it, received the result which is then inputted or automatically updated in the app.

Baroness Harding’s husband John Penrose, the Conservative MP for Weston-super-Mare, had previously been told to self-isolate by the Test and Trace app, after potentially coming into contact with someone who had coronavirus.

He tweeted on November 9: “It never rains but it pours…. my NHS app has just gone off, telling me to self-isolate, which I’m doing. No symptoms so far *crosses fingers*.”

Asked at the time if he had spoken to his wife about it, he told the PA news agency: “We are trying to make sure we are doing it by the book if I can put it that way.”