Leuser was first brought to the Medan quarantine centre in February 2004 after being intercepted by an SCOP team en route to Jakarta, where he was going to be taken as a gift. After several months of reintroduction training at a release site on the edge of Jambi's Bukit Tigapuluh National Park, Central Sumatra, he returned to the wild in December 2004

Photograph: Paul Hilton