AN IRA plot to blow up the British Parliament - using a barge packed with explosives and moored in the Thames - has been scuppered by British intelligence, according to reports in London last night. Details of the plot - a modern equivalent of the Gunpowder Plot of 1605 - have only just been disclosed. It was discovered when police searched the home of bus bomber Ed O'Brien after his death last month. O'Brien's modest flat in south London is turning out to be treasure trove of information about IRA plans, and the plot to blow up Parliament is the most spectacular of a number of the terror group's intentions revealed in the search. According to the Mail on Sunday , the plot to blow up Parliament had the potential to leave hundreds dead and injured. At any one time, when Parliament is sitting, there are more than 10,000 people in the highly ornate and historic Palace of Westminster. The Mail on Sunday says the plan was to detonate the barge when the House of Commons was at its busiest, the intention being to cause carnage on a massive scale. The IRA plan was also to destroy St Thomas' hospital on the opposite bank of the River Thames from Parliament. According to the Mail on Sunday, the documents uncovered by British intelligence show the intention was to park the barge packed with explosives only 300 metres from the Palace of Westminster. The projected amount of explosives would have created devastation across a 800-metre radius, the paper reports. News of the alleged plot was revealed as security experts took stock of what is believed to have been another IRA bomb - a small device that went off over the weekend in Old Brompton Road, West London. Beyond damaging a few cars and shattering a number of windows, the main effect of the bomb - planted in a litter bin outside a cemetery, and close to a Ministry of Defence building - was to create midnight panic as police moved in to evacuate local residents and throw a security cordon around the area.