The invites use American made-ink on English card (sweet) and are printed in gold and black, then burnished and gilded around the edge.
The Palace has confirmed that "around 600" have been invited to the service at St George's Chapel. There will also be a lunchtime reception at St George's Hall with a lemon elderflower" cake from London pastry chef Claire Ptak at Violet Bakery.
Among the reported guests are the Spice Girls, Elton John, Cressida Bonas and Chelsy Davy.
Save us a seat, will you, Harry?