The Invitation to William was a letter sent by seven famous Englishmen. They were later named the Immortal Seven. They sent this letter to William III, Prince of Orange, received by him on 30 June 1688 (Julian calendar, 10 July Gregorian calendar). In England a Catholic male heir to the throne, James Francis Edward Stuart, had been born. The letter asked William to force the ruling king, his father-in-law James II of England to make William's Protestant wife Mary, James's oldest daughter, the heir. This might possibly be done by saying that the newborn Prince of Wales was not really James' son.