Britons defied transport strikes and a gloomy economic outlook on Monday to register \"record-breaking\" levels of trade on the first day of post-Christmas sales. Despite a strike by drivers on the London Underground train network, Brent Cross mall in the capital\'s northwest announced sales of £1,000 per second as cash-conscious Brits flocked to grab a bargain. Thousands also lined up in Birmingham to get their hands on sales items at the Next and Selfridges stores. Upmarket retailer Selfridges confirmed that it had beaten the sales record for Boxing Day -- as the day after Christmas Day is known in Britain -- set in 2009. Trade at its stores in London, Manchester and Birmingham was up by 15 percent on 2009 figures, the company revealed. \"Despite Tube disruptions and launching our sale on a Sunday, we had record sales in our first hour,\" said Selfridges\' director of operations Sue West. \"Ladies\' accessories and jewellery have been the main attractions with high value diamond pieces driving Selfridges\' Wonder Room sales.\" Business on Oxford Street, central London\'s main shopping high street, was disrupted when a man was stabbed to death in broad daylight. Police made a number arrests after the man, believed to be in his late teens or early 20s, was killed near Bond Street underground station. In spite of the tragic interruption, retailers on the iconic London thoroughfare recorded strong sales. Jace Tyrrell of the New West End Company, which represents traders on Oxford Street, Regent Street and Bond Street, said home electrics and fashion accessories were \"flying off the shelves.\" Bluewater mall in southeast England said it expected almost one million bargain-hunters, lured by 80 percent mark-downs on some items. Some shops began slashing prices by more than 50 percent even before Christmas. London\'s underground train service was virtually halted by a strike over pay, with people forced to use buses or taxis to reach retail outlets. 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\". 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\".