Court case(1768) 4 Burr 2225

Peers executed a deed promising Catherine Lowe that he would not marry anyone but her, and that if he married any other woman he would pay her 1,000 pounds within three months. He did not promise to marry her, nor did she promise to marry him. He later married another woman, and she sued on the deed for the 1,000 pounds.

The Court of King's Bench, Lord Mansfield presiding, held the covenant void. It was not a mutual promise of marriage but a one-sided restraint on the defendant's liberty to marry, enforced by a penalty, and the law regards marriage as a matter of public interest which agreements may not fetter. The plaintiff could not recover the sum.