Beijing’s liaison office in Hong Kong and nearby police stations beefed up security on Sunday as thousands of extradition bill protesters gathered for another demonstration – which police had limited to a sit-in. Organiser Ventus Lau Wing-hong had said he would decide closer to the time whether to press ahead with a march from Chater Garden in Central to Sun Yat Sen Memorial Park in Western district, near the liaison office vandalised by protesters last weekend. But as crowds swelled, the…