Vesuvius may be the world's most monitored volcano but, for those watching, it's still a guessing game. Italian authorities insist they'll have several weeks notice before an eruption. But Prof de Vivo believes they'll have a day. "Not taking into account the worst case scenario is criminal". He's particularly concerned that the biggest hospital in Southern Italy is being built in the path of the last lava flow. "It's a totally crazy decision, probably dictated by political opportunity". Now, even the government's advisor, Prof Barberi, is recommending the evacuation period around Vesuvious be cut to three days.