A first aspect of the invention provides a gas or oil well tubing having an annular packer mounted thereon, wherein the annular packer is formed from an eutectic alloy. By prefabricating the annular packer on the tubing it can be placed in situ from the outset and thus can be active by melting at any time to form a eutectic seal quickly and easily. An annular packer with by-pass conduits is also provided to enable cement to be pumped past the annular packer when it is in situ. The annular packer is further provided with conduit clearance means to clear cement from within the conduits.