Hong Kong’s tourist arrival numbers have gone into free fall this month, dropping to a daily average of below 3,000 from about 100,000 in January, after temporary cross-border restrictions were put in place to fight the unfolding coronavirus outbreak.The Hong Kong Tourism Board revealed on Friday that the number of mainland Chinese visitors, who accounted for as much as 80 per cent of the city’s total arrivals before the outbreak of the disease now named Covid-19, fell to a daily average of 750…