The products were manufactured using Staeger's recycled PET and the brand's part owner, Bill Keeling, was impressed with the quality of the print and foiling, particularly the gold foil.
Prestat is chocolatier to the Queen and was established in 1902 by Antoine Dufour, the creator of the chocolate truffle. It has since been granted two Royal Warrants by Her Majesty the Queen and Her Majesty The Queen Mother.
Source:
http://www.packagingnews.co.uk/design/markets/chocolatier-to-the-queen-turns-to-staeger-for-new-packs/
