 In 1647 Charles , then a prisoner of Parliament , was brought to the castle for a period under arrest , before being moved to Hampton Court . In 1648 there was a Royalist plan , never enacted , to seize Windsor Castle . The Parliamentary Army Council moved into Windsor in November and decided to try Charles for treason . Charles was held at Windsor again for the last three weeks of his reign ; after his execution in January 1649 , his body was taken back to Windsor that night through a snowstorm , to be interred without ceremony in the vault beneath St George 's Chapel . 
