Beverage preparation with pressurized liquid

A beverage preparation apparatus for preparing a beverage by injection of pressurized water into a capsule having at least one flexible wall, said beverage preparation apparatus including a clamp assembly operable between an open configuration and a closed brewing configuration for beverage preparation, said clamp assembly comprising:

• a first clamp member having a recess in an inner wall thereof for receiving part of the capsule;
• a second clamp member comprising a rigid peripheral frame having a central void, and a resilient layer extending across said central void, whereby a front surface of said resilient layer defines a second inner wall for receiving part of the capsule, wherein respective inner walls of said first and second clamp members in said closed brewing configuration define a chamber for enclosing and supporting the capsule during beverage preparation;
• and
• a piston positioned in the central void of the rigid frame, said piston comprising a piston face for abutting a back surface of said resilient layer and a piston body, wherein said piston is resiliently coupled to said rigid peripheral frame to allow limited resilient movement of said rigid frame relative to said piston along a direction of closure of the clamp assembly.