The only indication left to William Dockwra's ingenious project, somewhere near Gracechurch Street, London.
 The London Penny Post was established in 1680 by William Dockwra, to supplement the service of the Royal General Post Office, which only operated between cities and towns.
(It started as a courier service for Royal purposes only, but soon the Royal purpose of making money inspired the Duke of York to make the services of the Royal Courier available for anyone who’s willing to pay for it.)
Trouble was, that the London Penny Post, charging one penny (from the receiver of the post) for a same-day delivery within the cities of Westminster, London and Southwark, only enriched Dockwra.
So in 1683 the English Monarchy claimed the business to itself, on the grounds that
Dockwra was circulating newsletters that were criticising the Duke of York. (William Dockwra, by the way, died a pauper.)
Successive governments started raising the prices, saying that the money is needed to finance the wars with France.
The tradition of raising prices under the pretext of war is still successfully practiced to this day, worldwide.