A beverage preparation capsule containing a beverage preparation ingredient, having a body with side walls formed from one or more substantially air- and liquid-impermeable sheet materials defining a chamber containing a beverage preparation ingredient and further defining an outlet channel having an upstream end in fluid communication with the chamber for escape of beverage from the chamber. At least a region of the outlet channel is filled by a filtration material for filtering the beverage escaping from the chamber. Also provided is a clamp assembly for preparing a beverage from such a capsule, the clamp assembly comprising two or more clamp members, wherein an inner wall of at least one of the clamp members comprises a concave base surface for receiving the capsule and one or more pressure pads projecting from the concave base surface for selectively constricting a region of the capsule.