J SAINSBURY has disclosed a massive provision for £30m to cover its investment in e-commerce. City analysts accordingly cut their profit forecasts for the current year by £45m to £615m - the latter figure being £300m down on predictions made in August 1998. Said one EC2 cynic: 'Maybe Sainsbury is planning the biggest ever thing to hit the internet - or perhaps it is just another way of losing £30m off the trading profit estimates.'