An undertaking may not be varied by a court, but the person making it may, on application, be released from its performance, often having offered an alternative, or on condition that a further undertaking is given (see Birch v Birch). In determining whether to exercise the discretion to release, where an undertaking could have been framed as a variable order (such as an order for sale under section 24A of the Matrimonial Causes Act 1973 (MCA 1973)), the court should apply the criteria of MCA 1973, s 31(7), which effectively requires an exercise balancing the competing interests of the parties. Such an exercise was carried out (though in a rather different case) by Cohen J in A v A (Financial Remedies: