the designs of barron and chubb were based on the use of movable levers but joseph bramah a prolific inventor developed an alternative method in  his lock used a cylindrical key with precise notches along the surface these moved the metal slides that impeded the turning of the bolt into an exact alignment allowing the lock to open the lock was at the limits of the precision manufacturing capabilities of the time and was said by its inventor to be unpickable in the same year bramah started the bramah locks company at  piccadilly and displayed the "challenge lock" in the window of his shop from  challenging "the artist who can make an instrument that will pick or open this lock" for the reward of £ the challenge stood for over  years until at the great exhibition of  the american locksmith alfred charles hobbs was able to open the lock and following some argument about the circumstances under which he had opened it was awarded the prize hobbs attempt required some  hours spread over  days