A method of forming a container, the method comprising the steps of: i) providing an injection moulded preform composed of a biaxially-orientable thermoplastic material, the preform being substantially planar and having a peripheral edge and a central portion; ii) clamping at least a portion of the peripheral edge of the preform in a frame; iii) heating the preform; iv) stretch blow moulding the heated preform, clamped with the frame, within a mould cavity defined by a first female mould to form an intermediate article having a bottom wall and an annular sidewall beneath an upper edge clamped within the frame, the stretch blow moulding step using a stretch rod to engage an inner side of at least the central portion of the preform and axially to stretch at least a part of the central portion of the preform prior to blowing a pressurized gas against the inner side which urges the opposite side of the preform radially outwardly against the mould; and v) shrinking the intermediate article, clamped with the frame, onto a second male mould to form a container having a bottom wall, defining a base, and an annular sidewall, defining a body portion, beneath the upper edge clamped within the frame, the container comprising biaxially oriented thermoplastic material in the annular sidewall and at least an outer portion of the bottom wall, characterised in that the frame comprises a pair of upper and lower mating frame members (10, 12) forming an opening in the frame, wherein the peripheral edge is clamped between the frame members and the central portion is located in the opening, and the frame is coupled to a heating device for heating the frame to a controlled temperature or the frame is coupled to a cooling device for cooling the frame to a controlled temperature. i) providing an injection moulded preform composed of a biaxially-orientable thermoplastic material, the preform being substantially planar and having a peripheral edge and a central portion; ii) clamping at least a portion of the peripheral edge of the preform in a frame; iii) heating the preform; iv) stretch blow moulding the heated preform, clamped with the frame, within a mould cavity defined by a first female mould to form an intermediate article having a bottom wall and an annular sidewall beneath an upper edge clamped within the frame, the stretch blow moulding step using a stretch rod to engage an inner side of at least the central portion of the preform and axially to stretch at least a part of the central portion of the preform prior to blowing a pressurized gas against the inner side which urges the opposite side of the preform radially outwardly against the mould; and v) shrinking the intermediate article, clamped with the frame, onto a second male mould to form a container having a bottom wall, defining a base, and an annular sidewall, defining a body portion, beneath the upper edge clamped within the frame, the container comprising biaxially oriented thermoplastic material in the annular sidewall and at least an outer portion of the bottom wall, characterised in that the frame comprises a pair of upper and lower mating frame members (10, 12) forming an opening in the frame, wherein the peripheral edge is clamped between the frame members and the central portion is located in the opening, and the frame is coupled to a heating device for heating the frame to a controlled temperature or the frame is coupled to a cooling device for cooling the frame to a controlled temperature.