The royal couple will travel 1,250 miles over the three-day tour, meeting care home staff, teachers, schoolchildren and volunteers to learn about the challenges they faced during the coronavirus pandemic.
They were clearly delighted as the 72-year-old Welsh singer performed his classic hit Merry Christmas Everyone on the platform at Euston station.
The Duchess, wearing an Alexander McQueen coat and tartan scarf, tapped her foot and swayed to the music as they waved to passengers from a balcony.
Mr Stevens said he was “over the moon” to be playing Merry Christmas Everyone for William and Kate, revealing that it was the first time he had played for royalty in his long career.
Mr Stevens was the biggest selling singles artist of the 1980s and his hits compilation Singled Out is currently at no.10 in the album charts.
Merry Christmas Everyone reached the top of the charts in 1985 – the fourth and last number one single for Stevens – real name Michael Barratt – and has since remained a firm festive favourite.
Before climbing aboard for their first journey on the royal train, they spent time chatting to staff from Transport for London, Network Rail and train operating companies about their experiences of working throughout the pandemic.
On behalf of the nation, they passed on their thanks for everything they have done to keep trains in London running and the measures taken to ensure passengers could travel safely with confidence.
The Duke told Alero Abbey, TfL area manager for Green Park and Euston: “It’s moments like this when people really appreciate what you do every day. Suddenly we all know what you do and that you do a really good job.”