He succeeded his brother in 1270 as Henri III Comte de Champagne et de Brie, Enrique I King of Navarre.
The Gesta Philippi Tertia Francorum Regis of Guillaume de Nangis records the death in 1274 of "Henricus rex Navarræ comesque Campaniæ in regno Navarræ". The necrology of Saint-Etienne, Troyes records the death "23 Jul" of "Henricus rex Navarre". 1
Henry I, byname Henry The Fat, Spanish Enrique El Gordo, French Henri Le Gros... king of Navarre (1270–74) and count (as Henry III) of Champagne....
He succeeded his eldest brother, Theobald II (Thibaut V), in both kingdom and countship in December 1270. By his marriage (1269) to Blanche, daughter of Robert I of Artois and niece of Louis IX of France, he had one daughter, Joan, whom, by the Convention of Bonlieu (Nov. 30, 1273), he promised to one of the two sons of Edward I of England, Henry and Alfonso. This would have led to a union of his dominions with English Gascony, but it came to nothing. King Henry died in 1274; both the English princes died in the next decade, and Joan was married in 1284 to the future Philip IV of France. 2
Recognized as heir presumptive during his brother's reign, Henry succeeded to the thrones of the Kingdom of Navarre and County of Champagne upon Theobald II's death in December 1270. Henry I's proclamation at Pamplona, however, did not take place till the following year, 1 March 1271, and his coronation was delayed until May 1273. His first act was the swear to uphold the Fueros of Navarre and then go to perform homage to Philip III of France for Champagne.
Henry came to the throne at the height of an economic boom in Navarre that was not happening elsewhere in Iberia at as great a rate. But by the Treaty of Paris (1259), the English had been ceded rights in Gascony that effectively cut off Navarrese access to the ocean (since France, Navarre's ally, was at odds with England). Henry allowed the Pamplonese burg of Navarrería to disentangle itself from the union of San Cernin and San Nicolás, effected in 1266. He also granted privileges to the towns of Estella, Los Arcos, and Viana, fostering urban growth. His relations with the nobility were, on the whole, friendly, though he was prepared to maintain the peace of his realm at nearly any cost.
Henry initially sought to recover territory lost to Castile by assisting the revolt of King Alfonso X of Castile's brother Philip in 1270. He eventually declined, preferring to establish an alliance with Castile through the marriage of his son Theobald to Alfonso X's daughter Violant in September 1272. This failed with the death of the young Theobald after he fell from a battlement at the castle of Estella in 1273.
Henry did not long outlive his son. He was suffocated, according to the generally received accounts, by his own fat. His only legitimate child, a one-year-old daughter named Joan, succeeded him under the regency of her mother Blanche. Joan's 1284 marriage to Philip the Fair, the future King of France, in the same year united the crown of Navarre to that of France and saw Champagne devolve to the French royal domain. 3