When Cecily was just six months old, both her father, Lord Harington, and grandfather, William Bonville, were executed following the disastrous Battle of Wakefield on 30 December 1460. The Bonvilles, having fought with the Yorkist contingent, were shown no mercy from the victorious troops of Margaret of Anjou (wife of King Henry VI of England), who headed the Lancastrian faction, and were thus swiftly decapitated on the battlefield. Cecily's maternal grandfather, Richard Neville, 5th Earl of Salisbury, was also executed after the battle which had been commanded on the Lancastrian side by Henry Beaufort, 3rd Duke of Somerset, while Richard Plantagenet, Duke of York, had led the Yorkists and was consequently slain in the fighting. Margaret of Anjou, Queen of England, was in Scotland at the time raising support for her cause and so had not been present at Wakefield. In less than two months, the Yorkists suffered another major defeat at the Second Battle of St Albans on 17 February 1461, and the Lancastrian army's commander Margaret of Anjou, in an act of vengeance, personally ordered the execution of Cecily's great-grandfather, William Bonville, 1st Baron Bonville, the next day. These executions left Cecily Bonville as the wealthiest heiress in England, having inherited numerous estates in the West Country, as well as manors in Lancashire, Lincolnshire, Yorkshire, and Cumberland. She succeeded to the title of "suo jure" 7th Baroness Harington of Aldingham on 30 December 1460, and the title of "suo jure" 2nd Baroness Bonville on 18 February 1461.