Hong Kong is famous for its urban landscape but locals love its trails: the MacLehose, Wilson, Hong Kong and Lantau trails wind upwards through mountainous jungle terrain and offer breathtaking views of land and sea. Every year upon the Lunar New Year holiday a select group of runners are invited to try and run all four trails - 298km in total - in one punishing ultramarathon. In 2021, an even smaller group are being called upon to try: Mark Agnew interviews runner Hyun Chang Chung about about…