A friend just asked me how the coffee in 18th century London coffee houses was prepared. I hazarded it was roasted in the City or in the individual shops, ground or mashed with a mortar and pestle, and then the grounds boiled loose with water and transferred into a serving jug. Does anyone really know?

Excellent question. From a 1652 pamphlet advertising London's first coffee stall:

"It is a simple innocent thing, composed into a drink, by being dryed in an Oven, and ground to Powder, and boiled up with Spring water, and about half a pint of it to be drunk...."

Some more interesting details here:

http://www.openculture.com/2012/07/the_ ... 1650s.html

And more about early coffee culture:

https://www.telegraph.co.uk/travel/dest ... feehouses/