Abstract: The present invention provides a downhole heating tool with an increased heating capacity for use in setting alloy plugs/seal in downhole target regions of wellbores, such as oil/gas wells. The increased heating capacity enables greater quantities of alloy to be melted in one operation. It also enables alloys with higher melting points to be melted in the downhole environment. To this end the heating tool comprises a plurality of discrete tubular heating units linked together by connection means that permit the movement of the tubular heating units relative to one another. The relative freedom of movement between the heating units facilitates a transition between a deployment configuration, in which the heating tool is optimised for deployment downhole, and a heating configuration, in which the heating tool adopts an expanded heating footprint within a downhole target region.