“I know I’ve been exposed to it from March 4,” the 47-year-old “Luther” star said — the same date he was photographed with Sophie Grégoire Trudeau, 44, at a packed charity event in London, alongside F1 star Lewis Hamilton.

“That’s when the person that came up positive, that was the time I got in contact with that person,” he said in a video update, again stressing that his “known exposure was March 4.”

Without naming the person, he revealed that he got tested after hearing about someone “also in the public eye” being infected.

He said he found out about it Friday — the morning he would have woken up to hear that Canada’s first lady had tested positive.

“On Friday last week I was told that someone that I had been in contact with had tested positive,” he said.

“And I’m on location, about to start a film and the news breaks that this person, who is also in the public eye, had tested positive.

“My job made me test immediately. I had to test because it meant putting a lot of people at risk — if I had been exposed, then the people I was working with would also have been exposed,” he said, saying he immediately quarantined himself at home.

“I wasn’t showing any symptoms but I am very glad I made that decision [to get tested] because I have been out of contact with everyone since.”

“The early testing is the way we need to approach this,” he said, highlighting the problem of the procedure proving difficult for many to get.

Elba said he was “feeling fine” if a little tired — but admitted he feared his asthma put him in the “high category of most at risk.”

“Of course I’m worried,” the star added. “Catching corona was definitely not on my bucket list at all.”

The actor laughed when a fan pointed out his wife, Sabrina Dhowre, 30, coughing in the background of his live video.

He said she had finally been tested, without a result being announced yet. “She’s doing OK,” he said, calling it “an amazing bonding time” for them as a couple.

Racing driver Hamilton, 35, has yet to comment on being in the same photo, hugging Elba alongside Trudeau at the We Day UK charity event.

He has posted a PSA on hand-washing, saying from his home, “The coronavirus is very, very serious.”