The Benchmark Sensex tumbled over 453 points -- its biggest single session fall in one year -- to close at 33,149.35 today on widespread selling triggered by widening fiscal deficit concerns. Official data showed the country's fiscal deficit at the end of October hit 96.1 per cent of the budget estimates for 2017-18. Investors also kept their portfolios at a low ebb ahead of second quarter GDP numbers. -- PTI