A stamp to celebrate Team GB's gold in the rowing men's four will be will be on sale by lunchtime tomorrow.
The honour will be the first time Royal Mail has issued stamps on a Sunday.
Royal Mail will produce the stamp - celebrating Alex Gregory, Pete Reed, Tom James and Andrew Triggs Hodge's success - within 24 hours.
A fleet of 90 Royal Mail vehicles will deliver the stamps to more than 400 post offices by lunchtime tomorrow.
This is the ninth gold medal stamp to be issued by Royal Mail.