Inspector Donaldson was killed during the Haslemere Riot on July 29, 1855.
A short ceremony was led by Reverend Canon David Wilbraham MBE on the Memorial Green, in front of the town hall.
In attendance were Henry Pelham – the great-great-great-grandson of Inspector Donaldson – Waverley Borough Commander Inspector Sam Adcock, Haslemere mayor Councillor Jacquie Keen, councillors and members of the public.