Capsules, apparatus, and methods for preparing a beverage

A clamp assembly for preparing a beverage from a capsule containing a beverage preparation ingredient, the clamp assembly comprising:

• a first clamp member and a second clamp member that define a clamp cavity for accommodating a capsule containing a beverage preparation ingredient, the clamp cavity having a first end defining an inlet for injection of water into the capsule and a second end defining an outlet for escape of a beverage from the capsule;
• at least one of the first and second clamp members comprising:
• an outer clamp shell having an inner side facing the clamp cavity, the inner side comprising a recess having a floor;
• and
• an insert at least partially disposed within the recess of the outer clamp shell, the insert comprising a base surface and at least one pressure pad extending from the base surface towards the clamp cavity in a direction away from the floor of the recess, wherein the at least one pressure pad comprises a convex exterior surface that faces the clamp cavity.