Catherine has slowly returned to public events after cancer treatment and had been expected in the procession of Royal Ascot, but she abruptly canceled.

Kate Middleton, the Princess of Wales, recently appeared alongside Prince William, as well as their children Prince George, Princess Charlotte and Prince Louis at Trooping the Colour.

Kate, who shares three young children with William, has made a gradual return to public engagements this year since announcing in January that she is in remission from cancer. Kate has not shared details of the type of cancer with which she was diagnosed, though she has shared she underwent chemotherapy treatment.