The King and Queen arrived as downpours swept across London and Charles was photographed waving to well-wishers. British King Charles returns to London for what is widely expected to be further treatment following his cancer diagnosis.Charles and Queen Camilla flew by helicopter to Buckingham Palace from their private Sandringham home on Tuesday and were driven the short distance to nearby Clarence House. It was announced last week that the head of state has a “form of cancer” and at the weekend he issued a statement praising “all those organisations which support cancer patients”. Charles had…