Mr Lee was among a small group of people who watched the NDP at the Star Performing Arts Centre that evening.
Most Singaporeans watching live television at home saw Mr Lee doing something many of them had become accustomed to doing after masks became mandatory because of the Covid-19 pandemic.
Mr Lee can be seen using his right hand to adjust his mask, which appears to have slipped down the nose. The screenshot is circulating on social media and messaging platforms like Facebook and WhatsApp.
The photo shows MPs Edwin Tong and Sun Xueling reciting the Pledge, with their right hands on their chests.
There was a similar mask moment on July 27 at the Swearing-In Ceremony of the Cabinet in the Istana. Mr Tan Chuan-Jin was filmed, face exposed, using both hands to adjust his mask.
Mr Tan said later on Facebook that he was making a knot as one of the elastic bands of the mask had snapped.
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