Historically, ExCo Senior Unofficial Member importance greatly exceeded that of the LegCo counterpart, thus their term of office were longer.
The first ethnic Chinese to be appointed LegCo Senior Unofficial Member was Ho Kai, who held the post from 1906 to 1914.
Prior to Chau Tsun-nin, Chow Shouson was also ExCo Senior Unofficial Member when he stood in for three months following Henry Pollock.
Pre-WWII ExCo and LegCo Senior Unofficial Member typically served renewable four- to five-year terms.
During colonial times, the Urban Council also had a post entitled "Senior Unofficial Member", with a similar role.
Of these, six have served as Senior Unofficial Members in both councils: Catchick Paul Chater, Sir Henry Pollock, Chau Tsun-nin, Kan Yuet-keung, Chung Sze-yuen and Lydia Dunn.