Edward of Westminster (killed at the Battle of Tewkesbury) was the only son of which English king?

Edward of Westminster (13 October 1453 – 4 May 1471), also known as Edward of Lancaster, was the only son of King Henry VI of England and Margaret of Anjou. He was killed aged seventeen at the Battle of Tewkesbury, making him the only heir apparent to the English throne to die in battle.

Henry VI (6 December 1421 – 21 May 1471) was King of England from 1422 to 1461 and again from 1470 to 1471, and disputed King of France from 1422 to 1453. The only child of Henry V, he succeeded to the English throne at the age of nine months upon his father's death, and succeeded to the French throne on the death of his maternal grandfather Charles VI shortly afterwards.