Complex sentence: He was deposed in circa 1090 by the Norman Robert Fitzhamon, lord of Gloucester who established a lordship based in Cardiff and subsequently conquered the low-land part of Glamorgan (the Vale of Glamorgan) which was parcelled out to his followers.
Split into simpler sentences: He was deposed in circa 1090 by the Norman Robert Fitzhammon, lord of Gloucester who established a lordship based in Cardiff. He subsequently conquered the low-land part of Glamorgan (the Vale of Glamorgan) which was parcelled out to his followers.