Sir John Byron was an ardent supporter of the king. he served as Sheriff of Notinghamshire in 1634, and MP from the same region in 1624 and 1628. he had no children, and upion his death in 1652, the title passed to his brother Richardf, who was the ancestor of the famous romantic poet, the 6th Lord Byron, "Mad, Bad, and dangerous to know!"
He commanded a troop of cavalry during the Bishop's War, and raised the first regiment of Royalist cavalry in August 1642. His regiment fought at Edgehill in 1642.
Byron and his regiment distinguished themselves at the battles of Roundway Down and 1st Newbury in 1643, Sir John commanding the cavalry wing in both battles. He was created a Baron by the King at the end of the year.
In late 1643, he became Filed Marshal in charge of the Royalist forces in Cheshire, Lancashire, and North Wales, gaining the nickname "Bloody Bragadaccio". He fought at Muiddlewich, Nantwich, Marston Moor,, and Montgomery.