A string of high-profile arrests and detentions of travellers is likely to cause a major downturn in tourism to the US, with latest figures already showing a serious drop-off, tourist experts said. Several western travellers have recently been rejected at the US border on increasingly flimsy grounds under Donald Trump’s immigration crackdown, some of them shackled and held in detention centers in poor conditions for weeks. Germany updated travel guidance for travelling to the US, warning that breaking entry rules could lead not just to a rejection as before, but arrest or even detention. Three German citizens have been held