Why did the capture of London by rebels force King John to negotiate?

The capture of London by rebel barons in May 1215 was a critical turning point that forced King John to negotiate. Following the outbreak of civil war earlier that year, the loss of the capital significantly undermined the king's position, compelling him to seek a settlement to resolve the widespread baronial discontent.1

This pressure led directly to the meeting at Runnymede on June 15, 1215, where King John accepted the terms outlined in the Articles of the Barons. These negotiations ultimately resulted in the sealing of the Magna Carta, a landmark document that ensured feudal rights and established that the sovereign was subject to the rule of law.12