A key-operated lock comprising: a housing; a core rotatably mounted in the housing; a plurality of master pins in a first configuration to allow a first patron key to open the lock; and a plurality of reconfigurable tumbler assemblies in a first arrangement to allow a first top-master key to open the lock; wherein the housing, the core, the plurality of master pins and the plurality of reconfigurable tumbler assemblies are configured to have: a key pull position in which at least the first top-master key and the first patron key are insertable into the lock so as to be able to lock and unlock the lock; a basic rekey position in which the plurality of master pins are reconfigured by inserting a second patron key into a second configuration, wherein in the second configuration, the first patron key is not able to lock and unlock the lock from the key pull position and the second patron key is able to lock and unlock the lock from the key pull position; and a top-master rekey position in which the reconfigurable tumbler assemblies are reconfigured by insertion of a change tool and a second top-master key into a second arrangement, wherein in the second arrangement the first top-master key and first patron key are not able to lock and unlock the lock from the key pull position and the second master key is able to lock and unlock the lock from the key pull position. a housing; a core rotatably mounted in the housing; a plurality of master pins in a first configuration to allow a first patron key to open the lock; and a plurality of reconfigurable tumbler assemblies in a first arrangement to allow a first top-master key to open the lock; wherein the housing, the core, the plurality of master pins and the plurality of reconfigurable tumbler assemblies are configured to have: a key pull position in which at least the first top-master key and the first patron key are insertable into the lock so as to be able to lock and unlock the lock; a basic rekey position in which the plurality of master pins are reconfigured by inserting a second patron key into a second configuration, wherein in the second configuration, the first patron key is not able to lock and unlock the lock from the key pull position and the second patron key is able to lock and unlock the lock from the key pull position; and a top-master rekey position in which the reconfigurable tumbler assemblies are reconfigured by insertion of a change tool and a second top-master key into a second arrangement, wherein in the second arrangement the first top-master key and first patron key are not able to lock and unlock the lock from the key pull position and the second master key is able to lock and unlock the lock from the key pull position. a key pull position in which at least the first top-master key and the first patron key are insertable into the lock so as to be able to lock and unlock the lock; a basic rekey position in which the plurality of master pins are reconfigured by inserting a second patron key into a second configuration, wherein in the second configuration, the first patron key is not able to lock and unlock the lock from the key pull position and the second patron key is able to lock and unlock the lock from the key pull position; and a top-master rekey position in which the reconfigurable tumbler assemblies are reconfigured by insertion of a change tool and a second top-master key into a second arrangement, wherein in the second arrangement the first top-master key and first patron key are not able to lock and unlock the lock from the key pull position and the second master key is able to lock and unlock the lock from the key pull position.