The Duke of Cambridge donned surgical scrubs to learn about the pioneering robotic surgery of a leading cancer hospital - then joked its surgeons were computer game fanatics.
Dressed in a blue top, trousers and cap, and wearing a pair of slip-on foam rubber Crocs, the future king was taken into the operating theatres of the Royal Marsden Hospital to watch tumours being removed from patients with the help of the machines.
The Da Vinci robot allows surgeons to remotely cut away the cancerous growths as they operate two handheld controls connected to a 3D monitor located a few feet away from the patient.
Dexterous consultants have been taught the skills needed to handle the robot which allows them to operate without resorting to major invasive procedures and William watched with fascination as Anne White, 67, from Newton Abbott, Devon, had a tumour cut away from her tongue.
He peered at the 3D monitor as lead surgeon Professor Vin Paleri talked him through the procedure and then later watched another operation to remove a tumour from the base of 63-year-old Charles Ludlow's oesophagus.
William, who is president of the Royal Marsden NHS Foundation Trust, talked about the skills of the surgeon when he met cancer patient Joe Omar, 63, and his wife Lynn, 59, and their daughter Leila, 27.
The Duke joked with the 63-year-old comparing the Da Vinci robot to a computer game, saying: "It's the same as the Playstation gear.
"You can see all the doctors have done Playstation. They let me watch but not to have a go."
Mr Omar, a retired anaesthetist from Sutton, south London, worked at the Royal Marsden in the 1980s where he met his radiographer wife, and was having tests after a tumour was removed from his bladder.
William told him: "It's fascinating watching the robot work, it's so precise, you see it up close and you can really see how the human body is and how it works.
"You're literally going right into the tumour so you see exactly with precision where the tumour is - it's incredible - I was really, really impressed with it."