A polio-stricken illegal mainland immigrant has been jailed for seven years for robbing a woman of a mobile phone and a ring on the day he sneaked into Hong Kong. Yeung Kam-tin, 25, was found guilty by District Court Judge Mary Yuen Lai-wah of robbery, possession of an imitation firearm and illegal entry into Hong Kong. Yeung, together with two other illegal immigrants, Mok Sze-man and a 15-year-old boy, robbed Cheung Bit-ying in August when she went for a walk near her home in Shek Wu Wai Tsuen, Lok Ma Chau. Yeung, who walks with a limp after contracting polio as a child, and the teenage robber slipped into Hong Kong on the same day as Mok by hiding under trucks crossing the border. During the brief holdup, Mok shoved Cheung to the ground, threatening her with a chisel. Cheung also saw Yeung holding a gun-like object, which turned out to be a cigarette lighter. The trio eventually snatched a Nokia mobile phone and a silver ring from Cheung and fled. Cheung immediately told her uncle about the robbery, who reported it to the police. The trio were arrested in Shek Wu Wai Tsuen within half an hour of the report. Mok and the teenager, who both pleaded guilty to charges of robbery and unlawfully remaining in Hong Kong, were sentenced to prison terms of four years and seven months and three years and nine months, respectively.