The 24-year-old, who lives in Boyn Hill Road, has won three equestrian gold medals at the London 2012 Games with her horse Janeiro, and a postbox in Maidenhead High Street will be transformed by the Royal Mail tomorrow to mark her success in the team open event.
Painting will begin at 10am.
First class stamps featuring Sophie's image will also be on sale in about 500 post offices across the UK tomorrow, and in a further 4,700 branches from Saturday.
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CCTV images have been released of men police would like to speak to in connection with a homophobic attack on a couple as they took a train home from a Valentine's Day meal.