Kate Middleton broke her cover this weekend and attended the annual Trooping the Colour parade, RadarOnline.com has learned – marking her first public appearance since the news of her startling cancer diagnosis broke earlier this year. In a surprising development to come after Kate announced her shocking cancer diagnosis in March, the princess appeared in London on Saturday to attend the annual military parade celebrating the monarch’s birthday. Kate, 42, was spotted riding in a car alongside her three children – Prince George, Princess Charlotte, and Prince Louis. She was also seen entering B…