By Tim Hanlon The Princess of Wales made a touching tribute to Diana at a last public appearance on Christmas Day before her cancer was revealed. Kate had abdominal surgery on January 19 at The London Clinic which was described as being successful before further tests discovered the cancer. A month before that surgery she had been pictured chatting with well-wishers who she greeted outside church in Sandringham. Clutching the hand of her daughter Princess Charlotte, she smiled for the cameras on the royals’ traditional Christmas walk. And along with her Alexander McQueen coat and customised Gi…