Sir John Heydon (died 1653) was an English Royalist military commander and mathematician,

Lieutenant-General of the Ordnance The Lieutenant-General of the Ordnance was a member of the British Board of Ordnance and the deputy of the Master-General of the Ordnance. The office was established in 1545, and the holder was appointed by the crown under letters patent. It w ...

at the outbreak of the

First English Civil War The First English Civil War took place in England and Wales from 1642 to 1646, and forms part of the 1639 to 1653 Wars of the Three Kingdoms. They include the Bishops' Wars, the Irish Confederate Wars, the Second English Civil War, the Anglo ...

Life

The second son of Sir

Christopher Heydon Sir Christopher Heydon (14 August 1561 – 1 January 1623) was an English soldier, Member of Parliament, and writer on astrology. He quarrelled with his family over its estates in Norfolk. Background Born in Surrey, Heydon was the eldest son ...

, in 1613 he was keeper of the stores in Sandown Castle,

Deal, Kent Deal is a coastal town in Kent, England, which lies where the North Sea and the English Channel meet, north-east of Dover and south of Ramsgate. It is a former fishing, mining and garrison town whose history is closely linked to the anchora ...

. He was knighted in August 1620. In 1627 he was appointed lieutenant of the ordnance in the place of his brother Sir William, who was killed in the expedition to the

Isle of Rhé An isle is an island, land surrounded by water. The term is very common in British English. However, there is no clear agreement on what makes an island an isle or its difference, so they are considered synonyms. Isle may refer to: Geography * Is ...

. Between 1627 and 1643 Heydon was actively occupied in furnishing men, provisions, arms, guns, and ammunition for the service of the king. When Charles I raised his standard at

Nottingham Nottingham ( , East Midlands English, locally ) is a city status in the United Kingdom, city and Unitary authorities of England, unitary authority area in Nottinghamshire, East Midlands, England. It is located north-west of London, south-east ...

on 22 August 1642, Heydon was in charge of cannon and ammunition at York. He soon joined the king, and accompanied the Royalist army from

Shrewsbury Shrewsbury ( , also ) is a market town, civil parish, and the county town of Shropshire, England, on the River Severn, north-west of London; at the 2021 census, it had a population of 76,782. The town's name can be pronounced as either 'Sh ...

towards London in October 1642. He acted as Lieutenant-General of the Ordnance with Charles's forces, and joined his Privy Council. He was made D.C.L. at Oxford on 20 December 1642. Heydon suffered for his support of the king, having his goods sequestrated. He died on 16 October 1653. Although it is important to distinguish Sir John from the astrologer John Heydon (1629-c. 1670), Lieutenant-General Heydon is also found to have developed alchemical theory and investigative practice.V. Keller, 'The authority of practice in the alchemy of Sir John Heydon (1588-1653)', ''Ambix'' (Society for the History of Alchemy and Chemistry), Vol. 59 no. 2 (November 2012)
pp. 197-217
(University of Oregon).

Notes

;Attribution {{DEFAULTSORT:Heydon, John Year of birth missing 1653 deaths Cavaliers