Gilbert de Clare, 4th Earl of Hertford, 5th Earl of Gloucester (1180 – 25 October 1230) was the son of Richard de Clare, 3rd Earl of Hertford, from whom he inherited the Clare estates. He also inherited from his mother, Amice Fitz William, the estates of Gloucester and the honour of St. Hilary, and from Rohese, an ancestor, the moiety of the Giffard estates. In June 1202, he was entrusted with the lands of Harfleur

Harfleur

-Population:-Places of interest:* The church of St-Martin, dating from the fourteenth century.* The seventeenth century Hôtel de Ville .* Medieval ramparts * The fifteenth century museums of fishing and of archaeology and history....

 and Montrevillers.

In 1215 Gilbert and his father were two of the barons made Magna Carta

Magna Carta

Magna Carta is an English charter, originally issued in the year 1215 and reissued later in the 13th century in modified versions, which included the most direct challenges to the monarch's authority to date. The charter first passed into law in 1225...

 sureties and championed Louis "le Dauphin" of France

Louis VIII of France

Louis VIII the Lion reigned as King of France from 1223 to 1226. He was a member of the House of Capet. Louis VIII was born in Paris, France, the son of Philip II Augustus and Isabelle of Hainaut. He was also Count of Artois, inheriting the county from his mother, from 1190–1226...

 in the First Barons' War

First Barons' War

The First Barons' War was a civil war in the Kingdom of England, between a group of rebellious barons—led by Robert Fitzwalter and supported by a French army under the future Louis VIII of France—and King John of England...

, fighting at Lincoln under the baronial banner.