The Duchess of Cornwall joked she had gone into self-isolation as she took shelter at the London Transport Museum.
Camilla stepped briefly into an old air raid shelter which was on display and quipped, in an apparent reference to coronavirus: “I’m self-isolating.”
She and the Prince of Wales were on a visit to the museum to help mark 20 years of Transport for London (TfL).
The duchess wore gloves during the engagement but Charles did not, and the couple shook hands with some of those they met.
It comes a day after the Queen unusually wore large white gloves at a Buckingham Palace investiture for what was believed to be the first time.
The Government has advised thorough hand-washing as efforts continue to stop the spread of the disease.
Charles and Camilla had enjoyed a ride to the museum on an electric bus, boarding the red double decker at a specially installed temporary bus stop outside Clarence House.
Seated at the front of the top deck, they took in views of central London which were somewhat obscured by the rain.
The environmentally friendly bus, accompanied by a police escort, took the couple, TfL staff and a group of schoolchildren on the 10-minute journey down Pall Mall and past Trafalgar Square to Covent Garden.
During a tour of the museum, the couple sat in a 1938 Tube carriage and recorded a message which will be played on the capital’s transport network at some stage later in the year.
They also met TfL apprentices and staff who have pioneered environmental and mental health schemes in the workplace, as well as crisis response staff, as they walked around the building with Mayor of London Sadiq Khan.
At one stage Camilla, who chatted to school pupils in a children’s section of the museum, sat down in the soft play area as the young people showed her the various activities on offer.
One little girl said she had been learning about environmental issues in school, telling Camilla: “Antarctica’s melting.”
Before unveiling a plaque to commemorate TfL’s two decades, Charles made a short speech praising the “pure genius” of how the operation works.
He told the various staff gathered: “It is remarkable how you do it, how you manage to make such an immense operation work so well.
“And how you also manage to do new projects, upgrading of stations and lines and everything else at the same time as providing the service to the public.
“It is, in my opinion, pure genius how you do it.”