On 13 Apr 1360 a freak weather event known as Black Monday Hailstorm occurred as the army of King Edward III of England (age 47) were camped outside Chartres [Map]. Thomas Beauchamp 11th Earl Warwick (age 47), William Bohun 1st Earl of Northampton (age 50), Henry of Grosmont 1st Duke Lancaster (age 50), Edward "Black Prince" (age 29) and Walter Mauny were present. Around one thousand English were killed, with up to six thousand horses. King Edward III of England (age 47) believed the event to be an Act of God and proceeded to negotiate with the French resulting in the Treaty of Brétigny.

On 28 Apr 1360 Guy Beauchamp died from injuries received during the Black Monday Hailstorm.