William and Kate stuck rigidly to advice about contact during their visit to an NHS 111 centre dealing with the virus crisis.
But one member of staff forgot the new rules when she asked the royal couple for a photograph and without thinking reached out to shake their hands.
“Don’t shake hands!” William remonstrated with a laugh as he brought down his other hand to cut her off.
But he swiftly added as they posed for a picture: “We can do a photograph if we are not within a metre of each other.”
Afterwards Courtney Campbell, 32, a supervisor, laughed off her mistake: “That was so funny. I went to shake the hand. Coronavirus!
“I guess it’s just polite, isn’t it? In the professional environment we are so used to being greeted and shaking hands with each other.”
During the tour William met call handler Paula White, who turned out to be a former telephonist at Buckingham Palace who met the duke when he was a baby.
He joked: “Was I behaving myself? A rowdy little child?”
Afterwards she said: “He said, ‘Was I well behaved?’. I said, ‘I can’t say sir – the press are here!’.”
She added: “I worked there when his mum was getting married.”
Diana used to go into the switchboard room, she said.
“She used to be taking calls with us. I saw the ring!” she added.
“He was just a little baby when she brought him down.”
She said having a visit from the couple was a big boost for staff morale.
“It’s lovely. It’s like a pat on the back. It just raises morale,” she added.
At one point William was talking to a staff member and got on to the subject of Star Trek.
After a bit of talk, he said: “I think we are all going to have a lot of TV to watch in the next few weeks.”