Before she left, Catherine hugged a woman who appeared to be a visitor.

“I’m sorry. I wish there was more I could do to help,” the princess told the woman.

“I wanted to come and show my support for the amazing work that’s going on here and for those who are going through treatment and having such a hard time.”

Catherine added: “Are you ok? Yes? There is light at the end of that tunnel. Very nice to meet you and best of luck. You are in the best of hands.”

A Kensington Palace spokesman said: “The princess wanted to make the journey to both show her gratitude to the incredible team, but also highlight the world leading care and treatment the Marsden provides.”

It’s almost a year since the princess’s health problems were first revealed – with an announcement last January that she had undergone abdominal surgery.

Catherine then announced in a video statement in March that she was in the early stages of receiving cancer treatment – and in September released a video saying that her chemotherapy had ended.

Since the end of her treatment she has gradually returned to more public events, including Remembrance Sunday and her Christmas carol concert at Westminster Abbey, which were seen as positive signs of her recovery.