A Chubb detector lock is a lever tumbler lock with an integral security feature, a re-locking device, which frustrates unauthorised access attempts and indicates to the lock's owner that it has been interfered with. When someone tries to pick the lock or to open it using the wrong key, the lock is designed to jam in a locked state until (depending on the lock) either a special regulator key or the original key is inserted and turned in a different direction. This alerts the owner to the fact that the lock has been tampered with. Any person who attempts to pick a detector lock must avoid triggering the automatic jamming mechanism. If the automatic jamming mechanism is accidentally triggered (which happens when any one of the levers is lifted too high) the lock-picker has the additional problem of resetting the detector mechanism before the next attempt to open the lock. This introduces additional complexity into the task, increasing the degree of lock-picking skill required to a level which few people have. The first detector lock was produced in 1818 by Jeremiah Chubb of Portsmouth, England, as the result of a government competition to create an unpickable lock. It remained unpicked until the Great Exhibition of 1851. Development In 1817, a burglary in Portsmouth Dockyard was carried out using false keys, prompting Her Majesty's Government to announce a competition to produce a lock that could be opened only with its own unique key. In response, Jeremiah Chubb, who was working with his brother, Charles, as a ship's outfitter and ironmonger in Portsmouth, invented and patented his detector lock in 1818. Building on earlier work by Robert Barron and Joseph Bramah, Jeremiah developed a four-lever lock that, when subjected to attempted picking, or use of the wrong key, would stop working until a special key was used to reset it. This security feature was known as a regulator, and was tripped when an individual lever was pushed past the position required to bring the lever in line to open the lock. This innovation was sufficient for Jeremiah to claim the £100 reward on offer (). A locksmith who was a convict aboard one of the prison hulks in Portsmouth Docks was given the Chubb lock with a promise of a free pardon from the Government and £100 from Jeremiah if he could pick the lock. The convict, who had successfully picked every