The couple involved in the case are U.S. citizens who married in Florida but moved to the Isle of Man a year later. During their marriage, they had five children in addition to children from previous marriages.

The husband has challenged a ruling by the Isle of Man Court of Appeal, which ruled that the agreement is unenforceable, The Times of London said. The wife is seeking 5.6 million pounds ($8.5 million) but would get only 2 million pounds ($3.5 million) under the agreement.

The case is now before the Privy Council, which hears arguments Thursday. Suzanne Withers, a London lawyer, said it is the first opportunity the law lords have had since a 1929 ruling to end the ban on enforcing prenuptial agreements.

"In that case, such agreements were judged to be contrary to public policy," she said. "This is a chance for the House of Lords to acknowledge the evolution of social values since then and to decide whether it is appropriate for couples to take control of their own destiny in the event of a divorce -- hopefully in one unified judgment."