A TAXI driver was robbed at knifepoint by two passengers - then tailed the thieves until police caught them, the District Court heard yesterday. Prosecutor Jenny Fung told the court Hui May-shing was forced to hand over $290 after picking up the men on the Sun Tin Wai estate, Sha Tin. The robbers fled with the cash, but Hui kept them in his sights and later saw them boarding another taxi. He followed the car and alerted the police by radio. The police stopped the car and arrested both suspects. One of the men, Yu Chi-ching, 26, admitted carrying out the crime to feed his drug habit and confessed to a series of similar attacks. Yesterday he pleaded guilty to four counts of robbery during April and May last year and was jailed for five years by Judge Gould. Two of the other attacks were allegedly carried out with an accomplice in Sha Tin and Tsing Yi, during which they stole $850. But the other robbery was committed alone on the Sun Tin Wai estate. Yu escaped with $680.