In 1989 the series commemorated the 800th anniversary of the institution of the London Mayoralty.

Before Mayors were introduced in 1189 Cities were governed by Sheriffs. The office of Sheriff or 'Shire Reeve', is more ancient than any other in the City, being mentioned in Anglo-Saxon laws of the 7th Century. The Sheriffs exercised the King's Authority in the City, collecting the royal revenues and enforcing the royal justice until the institution of the Mayoralty in 1189. The medal shows the City of London coat of arms positioned above the mayoral chain with the dates 1189 to 1989.