For 10 points, name this brother of Richard the Lionheart, who signed the Magna Carta in 1215.
This man was suspected of murdering his nephew Arthur after a raid on Mirebeau, and allied against Frederick II in support of Otto IV as Holy Roman Emperor. Otto lost the Battle of Bouvines, effectively ending this king's war against his rival Philip II Augustus and confirming his loss of most of England's French possessions. That disaster also prompted English barons to force him to sign a document limiting his power. For 10 points, name this brother of Richard the Lionheart, who signed the Magna Carta in 1215.
This man was suspected of murdering his nephew Arthur after a raid on Mirebeau, and allied against Frederick II in support of Otto IV as Holy Roman Emperor.
{John} I of England [or {John} Lackland]