When is a lot of people too many people? It is impossible to put a precise number on such things, but the debate about "overtourism" – the idea that famous places are being "loved to death" by the many visitors who crowd into, or through, them – is only likely to become noisier as 2019 continues. Barcelona and Venice have been just two cities to voice recent concern about the impact of travel on their quality of life – Italy’s great island oasis received 125,000 visitors on Easter Day alone last year – while the mayor of Matera, one of this year’s European Capitals of Culture, has suggested that he would rather there was no interest in his constituency, lest it harms its fragile, historic centre.