Feng Wei, the deputy director of the Hong Kong and Macau Affairs Office, said in March that he was fully prepared to accept the reality of young radicals winning Legco seats in the September election, but expected them to mature politically over time. The two Youngspiration lawmakers obviously crossed the line for Beijing. The pair have only played into the hands of mainland officials in favour of playing hardball with Hong Kong.

The oath-taking controversy also offers local officials and Beijing loyalists a golden opportunity to reassert the city’s “executive-led government” and deny the existence of separation of powers.

What’s in three words? Hong Kong debates whether principle of separation of powers applies to city

Amid criticism that the government’s filing for a judicial review of Legco president Andrew Leung Kwan-yuen’s decision to let Yau and Leung retake their oaths violated the principle of separation of powers, Rita Fan Hsu Lai-tai, Hong Kong’s sole representative on the National People’s Congress Standing Committee, said the Basic Law “makes no mention” of separation of powers. Former Basic Law drafter Maria Tam Wai-chu joined in, arguing that separation of powers was not how Hong Kong’s political structure was defined.

Whatever the label, Hong Kong’s political system is characterised by checks and balances and distinct roles among the executive, the legislature and the judiciary. Although late paramount leader Deng Xiaoping (鄧小平) said in 1987 that it would be inappropriate for Hong Kong’s political system to be based on “separation of powers”, Beijing went on to accept checks and balances among the three branches of government. The oath-taking fiasco has reignited debate on the issue and could eventually upset the fine balance between the three branches, particularly if Beijing steps in by interpreting the Basic Law if the local courts do not rule in favour of the Hong Kong government in the judicial review.

Some mainland officials have been gauging the opinions of Hongkongers from different sectors on likely candidates to be the next chief executive. Aware of the opposition to Chief Executive Leung Chun-ying, mainland officials who have been doing the intelligence gathering are particularly interested in how Hongkongers view Financial Secretary John Tsang Chun-wah and Chief Secretary Carrie Lam Cheng Yuet-ngor.

Be ‘responsible’, CY Leung says in veiled attack on potential chief executive race rivals John Tsang and Regina Ip

Fan was right in warning that Beijing might back a trusted candidate for next year’s chief executive race regardless of his or her popularity, if independence talk continued to gather steam. Leung stands to benefit, as Beijing has considered him trustworthy since the Occupy movement in 2014. The two localists may lose their seats, but all Hong Kong people are paying the price for their antics.

Gary Cheung is the Post’s political editor