Thomas Cook shares plunge after Citigroup's 'zero' valuation

Thomas Cook has seen its shares plummet by a further 40% after banking analysts cut their target price on the holiday firm's stock to zero.Citigroup downgraded its rating to "sell" in the wake of the latest profit warning by the world's oldest travel company, which had already led to a fall in its shares of almost 15%.It came a day after Thomas Cook reported a half-year loss of £1.46bn as it counted the cost of Brexit uncertainty causing UK consumers to delay holiday plans.