He found three parallel but different stories told by eye-witnesses and research­ers. According to French self-taught volcanologist and alpha male Haroun Tazieff, the cause was a small gas eruption in a nearby crater lake, whereas according to Icelandic and American scholars it was a deep belch from the lake that caused carbon dioxide to pour into the valley. Did the victims suffer burns or not? Did they smell sulphur or not? Politicians and local residents believe a French nuclear test like those carried out on Mururoa Atoll was to blame, or an Israeli bomb. Or were the gods angry because the number of sacri­fices to them was dwindling?

What is fact and what fiction? It is a question Westerman poses throughout the book, with his usual journalistic candour and eloquence. How do stories emerge and when do they become myths? Can myths be traced back to facts from the past? And what are the personal motives of the main players: ambition, conceit, empathy, mistrust, political calculation, missionary zeal, superstition, religious ecstasy? He quotes American researcher Joe Devine: ‘We must be careful not to arrange the facts so that they tell our story. We must give the facts time to tell us their own story.’

But ‘the facts are composting in the tropical heat,’ says Westerman, in one of his brilliant metaphors. This is Africa, where ‘rumours are the oxygen of society’; as French expert on sea earthquakes Olivier Leenhardt puts it: ‘Europeans are no less credulous. Take the resurrection of Jesus; that rumour has been doing the rounds for almost two thousand years.’ This touches upon one of the deeper layers in the book, since Westerman is not just in search of stories – he painstakingly demonstrates how myths create reality.

• Everyone has his own truth; stories mutate, evolve, move with the times and, although invented, have a powerful effect on reality.