On the night of 25-26 April 1986, unknown to most of the world, scientists were busy testing Chernobyl's reactor No 4 to determine whether its coolant pumps would keep running in the event of a loss of power. Within minutes of beginning the test, a power surge caused a chain reaction which lead to a massive explosion and meltdown of the reactor's core. Two days later Tass, the then-Soviet state news agency, acknowledged there had been an “incident”.
Given the political climate at…