Considers the value of exclusivity or lock-out agreements as an anti-gazumping protection, under which a vendor in return for some inducement from a prospective purchaser promises to negotiate in good faith with that purchaser alone. Examines the relevant case law. In "Walford v Miles" (HL, [1992] 2 AC 198), held that lock-out agreements were not too vague to be legally enforceable. In "Pitt v PHH Asset Management Ltd",(CA, [1993] 4 All ER 961), the claimant successfully sued the defendant company for damages for breach of the lock-out agreement and in "Tye v House" (ChD, Abs57790), it was held that a disappointed purchaser could not gain an injunction to prevent the vendor from selling to someone in breach of a lock-out agreement. In conclusion looks at "Dandara Holdings Ltd v Co-operative Retail Services Ltd " ([2004] EWHC 1476 (Ch), [2004] ALL ER (D) 246 (Jun)) where the court accepted the idea that damages for breach of a lock-out agreement can reflect loss of the chance of purchasing a property.