The English Treasury seems to have come into existence around 1126, in the reign of Henry I. The treasury emerged out of the royal household, and served as the location where the king kept his treasures. The head of the treasury was called the Lord Treasurer. Starting in Tudor times, the Lord Treasurer became one of the chief officers of state, and competed with the Lord Chancellor for the principal place.
Beginning in the 17th Century, the Treasury was frequently entrusted to a commission, rather than to a single individual, and after 1714, it was always in commission. The commissioners were referred to as Lords of the Treasury, and given a number based on seniority. Eventually, the First Lord of the Treasury came to be seen as the natural head of any minister, and from Robert Walpole on, began to be known, unofficially, as the prime minister. Before 1827, the First Lord of the Treasury, when a commoner, also held the office of Chancellor of the Exchequer, while if the First Lord was a peer, the 2nd Lord would usually serve as Chancellor. Since 1827, the Chancellor of the Exchequer has always been second Lord of the Treasury.