A method for forming an elongate support structure having a central hollow portion is disclosed including arranging an elongate core member to extend horizontally and then forming a core assembly by locating a first tensioning member at a first end where the first tensioning member including tensioning elements extending from the first end of the core member along the outside of the core member to a second tensioning member located at the second end of the core member. An external mold assembly is attacked to the core assembly between the first and second tensioning members to form a combined mold and core assembly and to also form a cavity extending around and along the central core member through which the plurality of tensioning elements extend. The tensioning elements are then tensioned and the combined mold and core assembly is then positioned in an upright orientation and concrete injected into the cavity formed between the elongate core member and the external mold assembly.