By Michael Holden and Kate Holton LONDON (Reuters) – Queen Elizabeth said she was humbled by the support she had received during her Platinum Jubilee after crowds of royal fans cheered her appearance on the balcony of Buckingham Palace, flanked by her heir Prince Charles and two other future kings. The 96-year-old monarch had withdrawn from several events during the four-day celebrations due to “episodic mobility issues”. On Sunday she was greeted by huge cheers, trumpets and a rendition of the national anthem before retreating inside. Wearing bright green, the queen smiled and waved as she ap…