NOTE 37. ADD: For a good example of the difference between a shared understanding and a convention which regulates the parties dealings see Bridgestart Properties Ltd v. London Underground Ltd [2004] EWCA Civ 793 in which both parties were unaware that a limitation period had expired but continued to negotiate the terms of statutory compensation. It was held that there was no estoppel by convention because there was no convention that E would not take any limitation defence. Nor was there any unequivocal representation which would give rise to a promissory estoppel.