Question: Johan van Banchem, was one of the leaders of the lynching of Johan de Witt and Cornelis de Witt on August 20, 1672, he was rewarded for this crime with an appointment as "baljuw" of The Hague by which office of steward, designated a medieval official and then a national leader, William III?

Context paragraphs:
Hendrik Verhoeff: Hendrik Verhoeff (around 1645 – 27 June 1710 in Utrecht) was a silversmith and schutter from The Hague who played a role in the assassination of Cornelis- and Johan de Witt on August 20 1672.

Jacob de Witt: Jacob de Witt, "heer van Manezee, Melissant and Comstryen" (born 7 February 1589 in Dordrecht – died 10 January 1674 in Dordrecht) was a burgomaster of Dordrecht and the son of a timber merchant.  He was also a younger brother of Andries de Witt and the father of Johan and Cornelis de Witt.

Stadtholder: In the Low Countries, stadtholder (Dutch: "stadhouder" , ] ), is an office of steward, designated a medieval official and then a national leader.

Johan van Banchem: Johan van Banchem (1615 - 4 October 1694 (buried)) was one of the leaders of the lynching of Johan de Witt and Cornelis de Witt on August 20, 1672.  He was rewarded for this crime with an appointment as "baljuw" of The Hague by Stadtholder William III.  After a few years in this function he was arrested and convicted for gross abuse of his office.  He was sentenced to death on November 26, 1680 by the "Hof van Holland" (the main court of law in the province of Holland), but appealed the verdict to the "Hoge Raad van Holland en Zeeland" (the supreme court of the Dutch Republic).  He died in jail before this appeal was finished.

Johan de Witt: Johan de Witt or Jan de Witt, "heer van Zuid- en Noord-Linschoten, Snelrewaard, Hekendorp and IJsselveere" (24 September 1625 – 20 August 1672) was a key figure in Dutch politics in the mid-17th century, when its flourishing sea trade in a period of globalisation made the United Provinces a leading European power during the Dutch Golden Age.  De Witt controlled the Netherlands political system from around 1650 until shortly before his death in 1672, working with various factions from nearly all the major cities, especially his hometown, Dordrecht, and the hometown of his wife, Amsterdam.

Johan de Witt Jr.: Johan de Witt Jr., heer van Zuid- en Noord-Linschoten, Snelrewaard and IJsselveere (1662–1701) was the son of Johan de Witt and his wife Wendela Bicker (1635-1668).  Having been part of the old Dutch patrician De Witt family, De Witt Jr. took a seat as secretary of the city of Dordrecht.

Johan Kievit: Johan Kievit (1627–1692) was an Orangist Rotterdam Regent, who may have been one of the instigators of the murder of former Grand Pensionary Johan de Witt, of the Dutch Republic, and his brother Cornelis de Witt on 20 August 1672, together with his brother-in-law, Cornelis Tromp.

Hans Bontemantel: Hans Bontemantel (24 January, 1613 - 8 June, 1688) was a Dutch merchant and for a long time a schepen of Amsterdam, where he was born.  He also served as acting-schout in 1672, whilst he was 'president-schepen'.  As a supporter of Johan de Witt's political system, he was one of the nine regenten dismissed on 10 September 1672 by stadthouder William III of Orange, at the same time as the dismissal of Lambert Reynst, Andries de Graeff and Pieter de Graeff.

Cornelis de Graeff: Cornelis de Graeff, also Cornelis de Graeff van (Zuid-)Polsbroek (15 October 1599 – 4 May 1664) was the most illustrious member of the De Graeff family.  He was a mayor of Amsterdam from the Dutch Golden Age and a powerful Amsterdam regent after the sudden death of stadholder William II of Orange.  Like his father Jacob Dircksz de Graeff, he opposed the house of Orange, and was the moderate successor to the republican Andries Bicker.  In the mid 17th century he controlled the city's finances and politics and, in close cooperation with his brother Andries de Graeff and their nephew Johan de Witt, the Netherlands political system.

HNLMS Johan de Witt (L801): HNLMS "Johan de Witt" (Dutch: "Zr.Ms.  Johan de Witt" ) is the second Landing Platform Dock (LPD) amphibious warfare ship of the Royal Netherlands Navy.  It is an improved design of "Rotterdam" , which was designed in conjunction between the Netherlands and Spain.  The ship, displacing 16,800 tons, was launched in February 2007.  The motto of the ship is "Ago Quod Ago", translated as "I do what I do".

Supporting paragraphs: Johan van Banchem Stadtholder
Answer: Stadtholder