In 1570, the Queen chose Walsingham to support the Huguenots in their negotiations with Charles IX of France. Later that year, he succeeded Sir Henry Norris as English ambassador in Paris. One of his duties was to continue negotiations for a marriage between Elizabeth and Charles IX's younger brother Henry, Duke of Anjou. The marriage plan was eventually dropped on the grounds of Henry's Catholicism. A substitute match with the youngest brother, Francis, Duke of Alençon, was proposed but Walsingham considered him ugly and "void of a good humour". Elizabeth was 20 years older than Alençon, and was concerned that the age difference would be seen as absurd. Walsingham believed that it would serve England better to seek a military alliance with France against Spanish interests. The defensive Treaty of Blois was concluded between France and England in 1572, but the treaty made no provision for a royal marriage and left the question of Elizabeth's successor open.