Unforeseen events which provoke global crises – such as Covid — have come to be known as ‘black swans’. By the same token, the end of 2022 has just been visited by a great big fluffy white swan.     Over the past 24 hours the main benchmark for European gas futures – the Dutch Title Transfer Facility (TTF), for gas to be delivered in February – has crashed below 80 Euros per MWh, taking it below the level it was on 23 February, the day before Russia invaded Ukraine.