A coupling mechanism for securing a first object to a second object, the coupling mechanism comprising: a lug configured to be formed on or secured to the second object, the lug being removably insertable along an insertion axis (A-A); a shuttle movable within the lug along the insertion axis (A-A); a first resilient biasing means arranged to bias the shuttle; a plurality of locking elements each movable radially in the lug with respect to the insertion axis (A-A), between a retracted position allowing free insertion and withdrawal of the lug, and an extended position; each locking element being both movable from the retracted position and retainable in the extended position by a first surface profile (a-b) of the shuttle; the coupling mechanism further comprising a movable stop (30, 32, 42, 44) having: a first position in which the biased movement of the shuttle along the insertion axis (A-A) is limited so that the locking elements interact with the first surface profile (a-b) of the shuttle, and a second position in which the biased movement of the shuttle along the insertion axis (A-A) is extended so as to cause the locking elements to interact with a second surface profile (b-c) of the shuttle whereby the locking elements move from their extended position to their retracted position, thereby allowing disconnection of the first and second objects; the coupling mechanism further comprising a well configured to be formed in or secured to the first object; the lug being removably insertable in the well along the insertion axis (A-A); whereby each locking element in its extended position projects into a recess formed in a side wall of the well so as to lock the lug in the well; and whereby the locking elements in their retracted position allow withdrawal of the lug from the well; characterised in that insertion of the lug into the well causes the first resilient biasing means to bias the shuttle away from a base of the well. a lug configured to be formed on or secured to the second object, the lug being removably insertable along an insertion axis (A-A); a shuttle movable within the lug along the insertion axis (A-A); a first resilient biasing means arranged to bias the shuttle; a plurality of locking elements each movable radially in the lug with respect to the insertion axis (A-A), between a retracted position allowing free insertion and withdrawal of the lug, and an extended position; each locking element being both movable from the retracted position and retainable in the extended position by a first surface profile (a-b) of the shuttle; the coupling mechanism further comprising a movable stop (30, 32, 42, 44) having: a first position in which the biased movement of the shuttle along the insertion axis (A-A) is limited so that the locking elements interact with the first surface profile (a-b) of the shuttle, and a second position in which the biased movement of the shuttle along the insertion axis (A-A) is extended so as to cause the locking elements to interact with a second surface profile (b-c) of the shuttle whereby the locking elements move from their extended position to their retracted position, thereby allowing disconnection of the first and second objects; the coupling mechanism further comprising a well configured to be formed in or secured to the first object; the lug being removably insertable in the well along the insertion axis (A-A); whereby each locking element in its extended position projects into a recess formed in a side wall of the well so as to lock the lug in the well; and whereby the locking elements in their retracted position allow withdrawal of the lug from the well; characterised in that insertion of the lug into the well causes the first resilient biasing means to bias the shuttle away from a base of the well. a first position in which the biased movement of the shuttle along the insertion axis (A-A) is limited so that the locking elements interact with the first surface profile (a-b) of the shuttle, and a second position in which the biased movement of the shuttle along the insertion axis (A-A) is extended so as to cause the locking elements to interact with a second surface profile (b-c) of the shuttle whereby the locking elements move from their extended position to their retracted position, thereby allowing disconnection of the first and second objects; the coupling mechanism further comprising a well configured to be formed in or secured to the first object; the lug being removably insertable in the well along the insertion axis (A-A); whereby each locking element in its extended position projects into a recess formed in a side wall of the well so as to lock the lug in the well; and whereby the locking elements in their retracted position allow withdrawal of the lug from the well; characterised in that insertion of the lug into the well causes the first resilient biasing means to bias the shuttle away from a base of the well.