Acol is the bridge bidding system that, according to The Official Encyclopedia of Bridge, is "standard in British tournament play and widely used in other parts of the world". It is basically a natural system using four-card majors and, most commonly, a weak no trump.
It is named after the Acol Bridge Club, previously located on Acol Road in London NW6, where the system started to evolve in the early 1930s. According to Terence Reese, its main devisers were Maurice Harrison-Gray, Jack Marx and S. J. Simon. Marx himself, writing in the Contract Bridge Journal in December, 1952, said: "...the Acol system was pieced together by Skid Simon and myself the best part of 20 years ago." In another account, Marx and Simon...
The first book on the system was written by Ben Cohen and Terence Reese. Skid Simon explained the principles that lay behind the system, and the system was further popularised in Britain by Iain Macleod. The Acol system is continually evolving but the underlying principle is to keep the bidding as natural as possible. It is common in the British Commonwealth but rarely played in North America.