"Kate asked what kind of music I'd been playing," Corporal Steve Johnson, an RAF recruitment officer from Newcastle, who is busking at Tube stations across London told the Press Association. "She asked me to play but then said don't because it's too busy.
"Kate was more interested in the music, while William was more concerned with the day itself and how the appeal was going. Lots of people are ecstatic to see them."
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The station, which saw 44m people commuters use it in 2016/2017, will be transformed into a dining room complete with Christmas decorations.
Part of the monster fatberg will go on display in the Museum of London, while the rest of it will be converted into biodiesel.
Major engineering projects at key London stations mean hundreds of trains will be cancelled or diverted.