Kate, Britain’s Princess of Wales, will not be at Royal Ascot on Wednesday, with a royal source citing her need for balance as she returns to public engagements after being treated for cancer last year.

Her husband Prince William, heir to the throne, is set to be part of the royal procession at the horseracing event in southern England later on Wednesday, alongside his father King Charles and Queen Camilla.

The royal source said Kate was disappointed not to be attending.

The princess has gradually been returning to her public royal role after completing a course of preventative chemotherapy last year to address the presence of an unspecified form of cancer.

Royal Ascot sees top horses from around the world compete over five days in races worth up to a million pounds.