A locking mechanism for aircraft landing gear has a hook (3) displaceable into and out of engagement with the landing gear capture pin (1). A roller (45) on a latch arm (40) engages a part (36) of the hook (3) to prevent it moving from a position where the pin (1) is retained. A linear solenoid (50) and a motor-driven rotatable cam (63) can both be operated independently to move the roller (45) out of engagement with the hook (3) and thereby allow a spring (35) to rotate the hook and release the capture pin (1).