A pipeline inspection tool has a spirally arranged series of blocks, with each block having a magnet and at least one magnetic flux sensor. An axially extending support may be provided which terminates in mounts and the series of blocks may be mounted between the mounts. The support may be arranged so as to permit bending of said series of blocks but resist torsion of said series of blocks. A supporting tendon may extend from a second of the mounts through a first opening in each block around a tendon supporting pulley of the first of the mounts and back through a second opening in each block to the second mount. A compression spring surrounding each arm of the tendon between the tendon support and the series of blocks. The magnet of each block may be arranged such that a like pole of each magnet is at one side of the series of blocks. The poles of each magnet may be longitudinally elongated and the longitudinally elongated poles may be directed along an axis of said tool. The magnetic flux sensors of each block may be between the poles of the magnet of each block.