During their time belowground in 1979, Eavis and his fellow cavers explored some 30 miles of passages—an unprecedented feat. Nearly 40 years later, wearing black tights in the hot syrup of morning, Eavis smiled at the memory.
"There's no expedition that's ever explored that much at one time," he said. "We did most of it standing up, you see."
Eavis paused, stared down at his tights, and bent at the waist. He picked a leech from his bootlace and flicked it into the jungle.
"Up to that point we were all just simple English cavers," he said. "Mulu transformed us."
The 1979 adventure set the stage for exploration in Borneo. Several caving teams have since made the long journey to Mulu, and Eavis himself has led many of them. For his 13th trip, in 2017, he organized a team of 30 cavers, including his son Robert and many Mulu veterans. In late March I reached him by phone in Kuching, a city on Borneo's west coast, as he traveled north to meet them.
"We will probably find somewhere near 30 miles of new cave passage," he said confidently. "And nobody ever does that. Except for me, I suppose."