Abstract: Method of lining a pipe. An outer pipe of ferrous metal is lined with a lining pipe of crosslinked polyethylene which is initially provided as a precursor lining pipe. The precursor lining pipe is initially made of cross-linked polyethylene with an external diameter equal to the internal diameter of the outer pipe. The initial pipe is then drawn through a die to form a pipe with a smaller diameter. The material of the pipe is memory material so that when it is melted it automatically expands to the original size. The precursor pipe is inserted into the outer pipe and melted by drawing a burner through it. The burner burns fuel gas supplied with combustion air through a hose by which the burner is towed. Hot products of combustion melt the polyethylene causing the precursor lining to expand automatically into the lining pipe. This is supported by gas pressure of a desired value inside the lining pipe until the polyethylene solidifies on cooling.