A key cylinder lock including: a first cylinder body and second cylinder body, connected by a connection member, the first cylinder body housing a first barrel, and the second cylinder body housing a second barrel; an unlocking cam located between the first cylinder body and the second cylinder body; the connection member featuring a fixed block extending from its side; the fixed block set between the first barrel of the key cylinder and the unlocking cam; the key cylinder additionally including: a first driving shaft which extends through a bore in the fixed block and torsionally connects the first cylinder barrel and the unlocking cam such that the first cylinder barrel can drive the unlocking cam between a locked and an unlocked position; a second driving shaft which torsionally connects the second cylinder barrel and the unlocking cam such that the first cylinder barrel can drive the unlocking cam between a locked and an unlocked position; and a sliding stop pin, the sliding stop pin being located within the unlocking cam initially set in a first position which allows the unlocking cam to rotate, and restrained in that position by the presence of the first cylinder body, and biased to a second position by a resilient member in which the unlocking cam preventing the rotation of the unlocking cam to an unlocked position, such that the sliding stop pin is urged to this second position in the case that the first cylinder body is broken off from the remainder of the key cylinder; wherein the sliding stop pin features at least one circumferential groove; and the unlocking cam features at least one lock-stopping channel formed in a radial direction in the unlocking cam, the lock-stopping channel being equipped with a lock-stopping resilient member and a lock shotpin; such that on the movement of the sliding stop pin from the first position, the lock shotpin engages with the lock-stopping channel and constrains the sliding stop pin in the second position. a first cylinder body and second cylinder body, connected by a connection member, the first cylinder body housing a first barrel, and the second cylinder body housing a second barrel; an unlocking cam located between the first cylinder body and the second cylinder body; the connection member featuring a fixed block extending from its side; the fixed block set between the first barrel of the key cylinder and the unlocking cam; the key cylinder additionally including: a first driving shaft which extends through a bore in the fixed block and torsionally connects the first cylinder barrel and the unlocking cam such that the first cylinder barrel can drive the unlocking cam between a locked and an unlocked position; a second driving shaft which torsionally connects the second cylinder barrel and the unlocking cam such that the first cylinder barrel can drive the unlocking cam between a locked and an unlocked position; and a sliding stop pin, the sliding stop pin being located within the unlocking cam initially set in a first position which allows the unlocking cam to rotate, and restrained in that position by the presence of the first cylinder body, and biased to a second position by a resilient member in which the unlocking cam preventing the rotation of the unlocking cam to an unlocked position, such that the sliding stop pin is urged to this second position in the case that the first cylinder body is broken off from the remainder of the key cylinder; wherein the sliding stop pin features at least one circumferential groove; and the unlocking cam features at least one lock-stopping channel formed in a radial direction in the unlocking cam, the lock-stopping channel being equipped with a lock-stopping resilient member and a lock shotpin; such that on the movement of the sliding stop pin from the first position, the lock shotpin engages with the lock-stopping channel and constrains the sliding stop pin in the second position. a first driving shaft which extends through a bore in the fixed block and torsionally connects the first cylinder barrel and the unlocking cam such that the first cylinder barrel can drive the unlocking cam between a locked and an unlocked position; a second driving shaft which torsionally connects the second cylinder barrel and the unlocking cam such that the first cylinder barrel can drive the unlocking cam between a locked and an unlocked position; and a sliding stop pin, the sliding stop pin being located within the unlocking cam initially set in a first position which allows the unlocking cam to rotate, and restrained in that position by the presence of the first cylinder body, and biased to a second position by a resilient member in which the unlocking cam preventing the rotation of the unlocking cam to an unlocked position, such that the sliding stop pin is urged to this second position in the case that the first cylinder body is broken off from the remainder of the key cylinder; wherein the sliding stop pin features at least one circumferential groove; and the unlocking cam features at least one lock-stopping channel formed in a radial direction in the unlocking cam, the lock-stopping channel being equipped with a lock-stopping resilient member and a lock shotpin; such that on the movement of the sliding stop pin from the first position, the lock shotpin engages with the lock-stopping channel and constrains the sliding stop pin in the second position.