The third and final presidential debate is scheduled for this week at the College of William and Mary in Williamsburg, Va. But Americans, with that dim sense of history so characteristic of this country, may well ask: William and Mary Who? To Britons, the royal couple have one unique claim to fame: They are the only joint rulers in English history. (They endowed the college in the colonies in 1693.)

Their life together had an inauspicious beginning: When England's Mary, the gentle daughter of the future James II, was told that marriage had been arranged with her first cousin, William of Orange, she cried for a day and a half. She also wept at her wedding in 1677, after which the couple were put to bed and King Charles II himself drew the curtains around them, exhorting: "Now, nephew, to your work. Hey! Saint George for England!" William was 27, Mary 15.

The couple took up residence in Holland where William busied himself with politics and his mistress, Elizabeth Villiers, who had been Mary's maid of honor. He was a cold, unsociable man who rarely lost his temper in public but who beat his servants in private. He was thin and suffered from asthma. She was tall (5'11"), good-looking and congenial and spent her time reading, gossiping and playing cards.

William became king of England in 1689 by ousting his father-in-law, James II, the younger brother of Charles II. Mary then looked upon England as a depraved country, full of debauchery and profanity. "My heart is not made for a kingdom," she said. Still, she occupied herself with rebuilding the royal houses. She and William set new styles with neat, red-brick homes, geometric gardens, evergreens and blue-and-white china.

She had no living children (two were stillborn), and she died of smallpox in 1694. William was shattered. He told a friend that during the course of their marriage he had never known "one single fault in her," and he regarded her death as punishment for his sins. When William died in 1702 after falling from a horse (the animal had stumbled in a mole hole), his courtiers found, tied to his arm, a ring ornamented with a lock of Mary's hair.