A lock for a gate or door, comprising: - a frame; - a dead bolt slidably mounted on the frame and arranged to slide between a retracted position and a projecting position; - locking means arranged to move up and downwards for locking the dead bolt in its retracted position and in its projecting position; - a dead bolt lever which is connected to the dead bolt and pivoted about a pivot with respect to the frame between a first extreme angular position, wherein the dead bolt is in its retracted position, and a second extreme angular position, wherein the dead bolt is in its projecting position; - a latch bolt slidably mounted on the frame between a retracted position and a projecting position and urged to its projecting position by a spring; - a second turn latch bolt lever pivotally mounted on the frame and arranged to move the latch bolt from the latch bolt projecting position to the latch bolt retracted position upon rotation; - a second turn latch bolt pusher connected to said second turn latch bolt lever and said dead bolt lever and arranged to rotate said second turn latch bolt lever to move the latch bolt from its projecting position to its retracted position; and - a key actuated cylinder provided with a rotary driving bit arranged to engage said locking means, to move these locking means upwards to unlock the dead bolt in its retracted and in its projecting position; said second turn latch bolt pusher, to move this second turn latch bolt pusher upwards to rotate the second turn latch bolt lever to move the latch bolt towards its retracted position; and said dead bolt lever to move the dead bolt from its retracted to its projecting position and vice versa, said dead bolt lever comprising a first engagement portion for engaging the rotary driving bit when said rotary driving bit is rotated in a first direction to rotate the dead bolt lever from its second into its first extreme angular position, and a second engagement portion for engaging the rotary driving bit when said rotary driving bit is rotated in a second direction, opposite to said first direction, to rotate the dead bolt lever from its first into its second extreme angular position, and said second turn latch bolt pusher comprising a second turn engagement portion for engaging the rotary driving bit when said rotary driving bit is rotated further in said first direction with the dead bolt lever in its first extreme angular position to move the second turn latch bolt pusher upwards, characterised in that said dead bolt lever comprises an auxiliary engagement portion for engaging the rotary driving bit when said rotary driving bit is rotated in said second direction to rotate the dead bolt lever from an angular position in between its first and second extreme angular positions into its second extreme angular position, said first engagement portion being located between said auxiliary engagement portion and said second engagement portion; and in that the second turn latch bolt pusher comprises a lateral engagement portion for laterally engaging a distal extremity of the rotary driving bit in case the rotary driving bit has passed the second engagement portion of the dead bolt lever and the dead bolt has not been locked by the locking means and moves back into the lock by an external force exerted onto its free extremity, which lateral engagement portion extends from said second turn engagement portion upto the dead bolt lever in the second extreme angular position of the dead bolt lever. - a frame; - a dead bolt slidably mounted on the frame and arranged to slide between a retracted position and a projecting position; - locking means arranged to move up and downwards for locking the dead bolt in its retracted position and in its projecting position; - a dead bolt lever which is connected to the dead bolt and pivoted about a pivot with respect to the frame between a first extreme angular position, wherein the dead bolt is in its retracted position, and a second extreme angular position, wherein the dead bolt is in its projecting position; - a latch bolt slidably mounted on the frame between a retracted position and a projecting position and urged to its projecting position by a spring; - a second turn latch bolt lever pivotally mounted on the frame and arranged to move the latch bolt from the latch bolt projecting position to the latch bolt retracted position upon rotation; - a second turn latch bolt pusher connected to said second turn latch bolt lever and said dead bolt lever and arranged to rotate said second turn latch bolt lever to move the latch bolt from its projecting position to its retracted position; and - a key actuated cylinder provided with a rotary driving bit arranged to engage