London\'s underground train service was virtually halted by a strike over pay on Monday, disrupting the start of the post-Christmas sales and sporting fixtures. Most lines were shut or operating a vastly reduced service, with people forced to use buses or taxis to reach shops which are desperate for business after disappointing sales in recent months. Members of the London Underground train drivers\' union ASLEF voted overwhelmingly to hold a 24-hour strike on December 26, a public holiday in Britain known as Boxing Day, and on three more dates in the coming weeks. Drivers are angry that their employer is refusing to give them extra pay and a day off for working on Boxing Day. The operator has described their demands as \"outrageous\". In anticipation of the strike, Premier League football club Arsenal postponed their Boxing Day fixture with Wolves by 24 hours, but Chelsea\'s match with London rivals Fulham went ahead on Monday. Despite the strikes, thousands of shoppers flooded into the recently opened Westfield centre in Stratford, east London, hoping to snap up a bargain in Europe\'s biggest shopping mall. Shops began slashing prices by more than 50 percent even before Christmas. The drivers\' union plans three more 24-hour strikes on January 16, February 3 and February 13 over the pay issue. ASLEF said it balloted 2,200 drivers on the Underground network, known as the Tube, and they returned a 92.3 percent vote in favour of action. Tube drivers also walked out on Boxing Day last year, crippling the Underground but failing to deter shoppers who flocked to the traditional sales. The London Chamber of Commerce and Industry accused the union of holding the British capital and its businesses \"to ransom through yet more Tube strikes\". \"Retailers have already had one of their toughest years with recent sales figures showing a decline year-on-year fuelled by poor consumer confidence, rising unemployment and mild weather,\" said the body\'s chief executive, Colin Stanbridge.