A releasable lock for a pipe cradle, the releasable lock comprising an elongate arm pivotally mounted at a first end to a pivot mount on a cradle frame, the elongate arm being pivotally mounted such that pivoting of the elongate arm about the pivot mount displaces the elongate arm between a first release position allowing removal or addition of pipes from/to the pipe cradle and a second, securing position in which pipes are secured in position in the pipe cradle, a releasable locking element housed in a region of the second end of the elongate arm, the releasable locking element, being moveable between a release position allowing pivoting of the elongate arm about the pivot mount to the first release position and an engagement position preventing said pivoting of the elongate arm and thereby securing the elongate arm in the second position, characterised in that the lock comprises an aperture along a length of an upwardly extending side portion of the pipe cradle, the aperture enabling movement of the elongate arm between (i) the first, release position in which the elongate arm leaves the aperture, and (ii) the second, securing position in which the aperture receives the elongate arm, and a pivotally mounted blocking plate disposed about a portion of the aperture, the blocking plate being pivotally movable between (i) a first position in which the blocking plate blocks the aperture and prevents pivotal movement of the elongate arm between the first, release position and the second, securing position, and (ii) a second position in which the aperture is clear and enables pivotal movement of the elongate arm between the first, release position and second, securing position. the elongate arm being pivotally mounted such that pivoting of the elongate arm about the pivot mount displaces the elongate arm between a first release position allowing removal or addition of pipes from/to the pipe cradle and a second, securing position in which pipes are secured in position in the pipe cradle, a releasable locking element housed in a region of the second end of the elongate arm, the releasable locking element, being moveable between a release position allowing pivoting of the elongate arm about the pivot mount to the first release position and an engagement position preventing said pivoting of the elongate arm and thereby securing the elongate arm in the second position, characterised in that the lock comprises an aperture along a length of an upwardly extending side portion of the pipe cradle, the aperture enabling movement of the elongate arm between (i) the first, release position in which the elongate arm leaves the aperture, and (ii) the second, securing position in which the aperture receives the elongate arm, and a pivotally mounted blocking plate disposed about a portion of the aperture, the blocking plate being pivotally movable between (i) a first position in which the blocking plate blocks the aperture and prevents pivotal movement of the elongate arm between the first, release position and the second, securing position, and (ii) a second position in which the aperture is clear and enables pivotal movement of the elongate arm between the first, release position and second, securing position.