Moved by the spirit of a 9-year-old cancer patient at the Royal Marsden Hospital in Sutton, the Duchess of Cambridge, Catherine Middleton, has written a personal note to the child praising his strength and promising to keep him in her prayers.

The duchess met Fabian Bate, who is suffering from leukemia, on Sept. 29, when she, along with Prince William, opened the new Oak Centre for Children and Young People at the hospital.

Catherine’s words were intended to boost Fabian’s morale and at the same side reveal a kind side of the duchess.

“Despite the enormously demanding course of treatment you are undergoing, I was so touched by your strength of character and delighted to hear the news that one of your big sisters will be able to donate bone marrow to you later this year,” wrote Kate.

“I will keep my fingers crossed that your health goes from strength to strength over the months ahead, she added.

The duchess praised and showed her belief in the works of the Royal Marsden, whose president is her husband, Prince William, the Duke of Cambridge.

“This must be a troubling time for you, your parents and your sisters, but I know I left the Royal Marsden assured by how incredibly talented, kind and clever the team at the hospital are, the duchess continued.

“Combined with your belief and positive energy, you couldn’t be in better hands,” she reiterated.

“I will keep you and your family in my thoughts and prayers,” Catherine signed off.

The royal couple made their first visit since their marriage to the hospital last month.

Kate’s letter is seen as her first solo act of charity since marrying into Britain’s royal family.