A beverage producing system comprising: a capsule containing beverage ingredients; and a beverage preparation machine; the capsule comprising a cup-shaped body and a lid; the cup-shaped body having a base and a side wall and the lid being sealed to the cup-shaped body; the capsule being designed for insertion into the beverage preparation machine to permit a pressurised liquid to be flowed through the capsule in order to produce a beverage from interaction with the beverage ingredients; the beverage preparation machine having an enclosing member adapted to be selectively movable between an open position to permit insertion of the capsule into the beverage preparation machine and a closed position in which the enclosing member sealingly engages the capsule; wherein, prior to insertion, the side wall comprises: - an annular trough being dimensioned to receive the enclosing member on movement of the enclosing member into the closed position; - a first side wall section extending between the base and the annular trough; and - a second side wall section extending between the annular trough and a rim of the capsule, wherein the side wall is adapted to undergo plastic deformation during closure of the enclosing member, wherein the annular trough is adapted to form a sealing interface with a leading edge of the enclosing member, wherein, prior to insertion, the annular trough comprises an inner wall, an outer wall and a floor, wherein the rim is formed integrally with the cup-shaped body, wherein the rim is formed by a rolled-over portion of the side wall, wherein the cup-shaped body is formed from aluminium or an aluminium alloy, wherein the cup-shaped body is formed from a single integral piece of material, and wherein a thickness of the cup-shaped body is in the range of 80 to 120 microns. a capsule containing beverage ingredients; and a beverage preparation machine; the capsule comprising a cup-shaped body and a lid; the cup-shaped body having a base and a side wall and the lid being sealed to the cup-shaped body; the capsule being designed for insertion into the beverage preparation machine to permit a pressurised liquid to be flowed through the capsule in order to produce a beverage from interaction with the beverage ingredients; the beverage preparation machine having an enclosing member adapted to be selectively movable between an open position to permit insertion of the capsule into the beverage preparation machine and a closed position in which the enclosing member sealingly engages the capsule; wherein, prior to insertion, the side wall comprises: - an annular trough being dimensioned to receive the enclosing member on movement of the enclosing member into the closed position; - a first side wall section extending between the base and the annular trough; and - a second side wall section extending between the annular trough and a rim of the capsule, - an annular trough being dimensioned to receive the enclosing member on movement of the enclosing member into the closed position; - a first side wall section extending between the base and the annular trough; and - a second side wall section extending between the annular trough and a rim of the capsule,