The road wraps around the overgrown slopes, and it’s easy to see how the Ma Gong could have stayed hidden so long, beneath the green fog of vegetation. “They sent planes out—the Thai air force,” says Gaolan when he asks, “but we always managed to avoid them. They just dropped bombs at random onto the canopy.”

She drops him off not at the next village, as he expected, but in front of a cave just outside. He looks at her askance and she waves him in. “Xiongmin works inside. You’ll see.”

This is some sort of underground museum, it turns out. Not secret, literally underground, lit by orangey halogen lamps. He goes up to the counter for a ticket (priced in both ringgit and baht). The woman there also tries to entice him into buying some incense.

“I didn’t know you Communists were religious.”

“We’re not, but you might be.” She smiles at him. “The tourists kept asking for an Earth God shrine, so we set up one down the hill. It’s a Malaysian-Chinese thing: wherever they go, they want to pray to the local gods.”

He refuses the incense, and instead browses a rack of memorabilia—khaki caps with red stars on their crests, postcards of old propaganda posters. A little Mao statue seems like the perfect gift for Janet, and if it annoys Winston that’s a bonus.

Xiongmin is waiting just inside, and is expecting him. They shake hands gravely. “I mostly look after the archives,” he says, “but Gaolan says you’re a special visitor, so I thought I’d show you round myself.”

They walk down the tunnel, which Xiongmin explains was built as a refuge. “We had to hide from the bombs, and what if the army came? So we dug this with nothing, just a changkol blade and baskets to clear the soil away. We had to go back out every half hour for air, or we’d have fainted.” Henry pats a packed-earth wall as he walks past. It is cool and firm, like a real cave. There are alcoves for sleeping in, storage niches, and even a larger chamber with a peaked roof. “The radio room,” says Xiongmin. “We had a wire leading up to the surface.”

There is a whole warren of these underground passageways, now fitted with information boards and displays. A map marked with different colours shows how the area occupied by the Ma Gong shrank over time. There are entire walls of propaganda materials, posters and pamphlets emblazoned with revolutionary youths. And photographs, some posed, some candid—the comrades doing surprisingly ordinary things.

“Are those people…gardening?” It seems so unlikely.