An assembly 2 comprises a rigid, self-supporting AM component 4 which is in the form of a T-shaped pipe having an elongate section 6 which is open at its ends 8, 10 and a section 12 which extends transversely to elongate section 6 and opens at its end 13. The component 4 forms internal walls of a capsule which is subjected to Hot Isostatic Pressing (HIP). External walls of the capsule are defined by sheet metal sections (referenced 14 in FIG. 1 and described in more detail with reference to FIGS. 3 to 5) and are arranged to define the outer shape of at least a portion of a final component made by HIP. Between its inner and outer walls a void is defined into which powdered metal 16 is introduced so the capsule encases the powdered metal 16. In use, the assembly is subjected to HIP and, thereafter, the sheet metal sections of the capsule are removed to define a final component comprising both the AM component 4 and HIPed powder 16.