The Invitation to William was a letter sent by seven notable Englishmen, later named the Immortal Seven, 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, and the letter asked William to force the ruling king, his uncle and father-in-law James II of England, by military intervention to make William's Protestant wife Mary, James's eldest daughter, heir, on the grounds that newborn Prince of Wales was allegedly an impostor.