The worst railway disaster in New Zealand’s history occurred on Christmas Eve 1953, when the Wellington–Auckland night express plunged into the flooded Whangaehu River, just west of Tangiwai in the central North Island. Of the 285 people on board, 151 were killed. The cause of the tragedy was a volcanic lahar from the Mt Ruapehu crater lake, which sent a huge wave of water, silt, boulders and debris surging down the Whangaehu River minutes…