The founder and chief of the global communications group behind MediaCom, Mindshare and Mediaedge:cia, is set to receive the honour at a Guildhall ceremony that dates back to 1237. He was nominated by the Lord Mayor of the City of London, Alderman Ian Luder, and Alderman Alison Gowman.
A number of ancient privileges associated with the Freedom include the right to herd sheep over London bridge, to go about the City with a drawn sword, to be married in St Paul's Cathedral, buried in the City and, if convicted of a capital offence, to be hanged with a silken rope.
Going into a year expected to be punctuated by tough media trading conditions, other ancient rights that would arguably be more useful include the right to avoid being press-ganged, and to be drunk and disorderly without fear of arrest.
The Lord Mayor said: "Sir Martin is one of the best known names in advertising and communications and his success in developing WPP into a major international force is unparalleled. He is a great ambassador for British business across the world."
The medieval term "freeman" meant someone who was not the property of a feudal lord, but enjoyed privileges such as the right to earn money and own land.
Sorrell founded WPP in 1985 and has been chief executive throughout its history. The group is now among the world’s leading communications services groups, employing 102,000 people (including associates) in more than 2,000 offices in 106 countries.
Other famous honorary freemen include The Queen, Florence Nightingale, General Dwight Eisenhower and Theodore Roosevelt.
This article was first published on mediaweek.co.uk