Yeung Sum obtained his undergraduate degree at the
University of Hong Kong. He was a residential member in ''St. John's College'' and became the president of its student association from 1972–1973. He gained his master's degree at the
University of York in Britain before returning to earn his doctorate from the University of Hong Kong. Yeung Sum has taught at the University of Hong Kong since 1979 and has been a lecturer in the Department of Social Work and Social Administration since 1985. When the issue of Hong Kong sovereignty after 1997 came up in 1983, Yeung and some graduates from the University of Hong Kong founded
Meeting Point, the first political organisation supporting Hong Kong's return to Chinese sovereignty. During the drafting of the
Hong Kong Basic Law, he pushed for a democratic model for Hong Kong after 1997. He was the second chairman of the group from 1988 to 1989. He also formed the
Joint Committee on the Promotion of Democratic Government with liberal-minded drafters
Martin Lee and
Szeto Wah and became the spokesman of the committee. He was a committee member of the
Hong Kong Alliance in Support of Patriotic Democratic Movements in China during the
Tiananmen protests of 1989 and remained critical of the Chinese government after the bloody crackdown. In 1990, he became the founding vice-chairman of the
United Democrats of Hong Kong, the first pro-democracy party and filled candidates in the
District Board elections and
Urban and Regional Councils elections. In the
first Legislative Council direct election, he was directly elected through the
Island West constituency. He became the vice-chairman of the
Democratic Party when the United Democrats and Meeting Point merged in 1994. Yeung remained legislator until the legislature was dissolved in 1997 when Hong Kong was handed over to China. He was re-elected to the Legislative Council in the
1998 LegCo election and remained in the LegCo until he stepped down as the second place on the party's candidate list in 2008 behind
Kam Nai-wai. Yeung represented the Mainstreamers, a relatively moderate faction, within the democratic camp, and discontent with him within the Democrats led to splits within the party. When Yeung took the chairmanship from Martin Lee in 2002, legislator
Albert Chan quit the party, and the following year a number of "Young Turks" left the party to join
The Frontier. In 2004, taking responsibility for recent
election failures, he announced that he would not seek another term as party chairman. He has remained on the party's central committee and executive committees occasionally. On 28 February 2020, Yeung was arrested over his involvement in a march on 31 August 2019 which was part of
protests sparked by the extradition bill, and had been classified by police as illegal assembly. A few hours later, he was released on bail, as were the other arrestees
Jimmy Lai and
Lee Cheuk-yan. The cases were scheduled to be heard at Eastern Law Court on 5 May 2020. On 18 April, Yeung was again arrested as one of 15 Hong Kong high-profile democracy figures, on suspicion of organizing, publicizing or taking part in several unauthorized assemblies between August and October 2019 in the course of the anti-extradition bill protests. Following protocol, the police statement did not disclose the names of the accused. On 10 June 2022, Sum, along the two other pro-democracy figures, had his
Silver Bauhinia Star honour removed, and his Justice of the Peace appointment was revoked by the government due to his jail sentences related to anti extradition-bill protests. ==See also==