“Last” King of England before the start of The English Civil Wars (1642-47), Charles I was descended from The House of Stuart (the Dynastic House which had been defeated by The Tudors, but rose again after Elizabeth I left no Heirs). He became embroiled in Politics with Parliament over his Royal Power (which Parliament had begun to slowly erode in favor of a much wished “Constitutional Monarchy). Charles fought back with a “Loyalist” Army against The Parliamentarians (derided as “Roundheads” for their Protestant religious hairstyles). The resulting (2) Civil Wars would lead to Charles being captured, tried and executed by a Parliament Government which would declare itself The Commonwealth.
As we have seen, most English Monarchs used “Personal Banners” when they went into Battle or flown over their official Residences. Most maintained a similar design pattern, as first created by William The Conqueror around 1066 AD.
Charles I broke somewhat with tradition, by using a more “modern” non-Bunted “Swallowtail” design (very similar to a Guidon). It was an elongated style with twin “splits”. The entirety of this Field was Red. The far Hoist Canton was a White Field with the Red Cross of George.
The Royal Crest of Charles I (which featured mostly House of Stuart imagery), was placed near The Hoist as well. A “Human Hand” was also placed (by The 2nd Civil War), to symbolize Charles I “rightful” Position as “King of England”, as was the Banneroll of "Give Unto Caeser His Due" Although the original was destroyed, with the Restoration of The Monarchy in 1660 – Charles II (Charles I Son), also restored his Father's Banner (briefly).