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 cup-shaped body is formed from aluminium, an aluminium alloy or a laminate comprising at least one layer formed from aluminium or an aluminium alloy; wherein the first side wall section, annular trough and second side wall section are formed integrally; and wherein the annular trough is adapted to form a sealing interface with a leading edge of the enclosing member, and the side wall is adapted such that during closure of the enclosing member the side wall is plastically drawn over the leading edge of the enclosing member. 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; wherein the cup-shaped body is formed from aluminium, an aluminium alloy or a laminate comprising at least one layer formed from aluminium or an aluminium alloy; wherein the first side wall section, annular trough and second side wall section are formed integrally; and wherein the annular trough is adapted to form a sealing interface with a leading edge of the enclosing member, and the side wall is adapted such that during closure of the enclosing member the side wall is plastically drawn over the leading edge of the enclosing member.