General Notes

Geoffrey de Mandeville, who like his fellow (the 2nd (meaning Algernon Capell, 2nd Earl of Essex of the 1641 creation)) Earl of Essex of the present creation was Constable of the Tower of London, was created Earl of Essex in 1140 by King Stephen.  He already held numerous manors in Berks, Bucks, Essex, Herts, and Middlesex, which had belonged to his grandfather, another Geoffrey, at the time of the Domesday Survey in 1086.  The family originated in Normandy, but precisely where is unclear, since there are several place names there akin to Mandeville (which seems originally to have been in Latin 'Magna Villa' or "Great Town").  De Mandeville later sided with the Empress Maud, who granted him a more generously framed charter, including a clause making the post of Constable of the Tower hereditary.  Later still de Mandeville again sided with Stephen but subsequently rebelled yet again.  His son was recreated Earl of Essex by Maud in Jan 1155/6, the rebellious habits of the father and perhaps also the appointive nature of earldoms at the time requiring a regrant.

After the death of the 3rd de Mandeville Earl, right to the title passed through a female branch but these descendants of the original de Mandevilles took the old family name (Mandeville) and were recognised as Earls of Essex in the time of King's John and Henry III.  [Burke's Peerage, page 1004]

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following copied from James Stevens, World Connect db=:2052409, rootsweb.com
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Cokayne's "Complete Peerage" (Essex, pp. 113-116), says that, for reasons that are somewhat obscure, KING STEPHEN, made him Earl of Essex, then proceeds to detail Geoffrey's frequent switching of support for the EMPRESS MAUD and for KING STEPHEN in their contest for the throne.  About Oct 1143, he was accused of treason, but he ridiculed the charge.  He was, however, arrested and imprisoned until he surrendered his castles to avoid being hanged.  He then broke into open revolt, seized and fortified the Abbey of Ramsey, sacked Cambridge, and ravaged the fen country, until, when beseiging Burwell Castle, having removed his headpice on account of the heat, he was mortally wounded by an arrow.