A threatened to break a contract unless B agreed to a modification of it, which B did, before seeking a declaration that the modification of the contract was void under economic duress. In this case the threat to breach was NOT economic duress because there was no contemporaneous evidence that the threat had actually put B under duress.
Dyson J: In determining whether there has been illegitimate pressure, threatened or actual breach of contract is only one of several factors e.g. good faith, realistic practical alternative for D, protest by the victim, and whether D sought to rely on or affirm the contract. Had there been duress, he would have voided the contract.