Jacksons of Piccadilly is a London tea house, begun by Robert Jackson in 1815. It is now a brand owned by R. Twinings and Company Limited. It has earned several Royal Warrants, from Queen Victoria, King George V and numerous other royals through the 19th and 20th centuries.
The company also claims (although this is contested) to have invented the "original" recipe for Earl Grey tea, Lord Grey having given the recipe to Robert Jackson & Co. partner George Charlton in 1830. According to Jacksons, the original recipe has been in constant production and has never left their hands. Theirs has been based on China tea since the beginning.
References
Jacksons of Piccadilly Wikipedia(Text) CC BY-SA