’No greater liability’ clauses are a common feature of collateral warranties and third party rights memoranda. Their purpose is to ensure that the warrantor/promisor does not have greater exposure under the third party rights granted than it has under the original contract. However, the drafting of these clauses has been subject to debate and can sometimes result in unintended consequences for the parties. Collateral warranties—general principles It is a generally accepted commercial principle, among users of collateral warranties, that, if a party enters into a warranty which is collateral to an underlying contract, it should not be under any obligations or duties under that warranty that are greater or of a longer duration than those under the original contract. In fact, professional indemnity insurance policies commonly exclude cover for claims under a collateral warranty that result from obligations that are more onerous than those under the original or underlying contract. In British Overseas Bank v Stewart Milne the court recognised that the underlying commercial purpose of collateral warranties