Royal Bank of Scotland slid to a pretax loss of £678mn ($1.1bn) in the second quarter, bruised by writedowns on Greek government bonds and Irish customers struggling to repay loans.RBS chief executive Stephen Hester said his own investment bankers had retreated to much more defensive positions in recent months: “These are markets to be careful, not to try and be a hero,” he said yesterday.His bank fell into the red after posting a £1.17bn profit a year ago, hit by impairments on bad loans of almost £2.3bn. That was up from £2bn in the first quarter but a little better than 2.5bn a year earlier.The bank wrote off £733mn to cover anticipated losses on its £1.45bn Greek bond portfolio.It also said the impairment charge at its Ulster Bank operations in Ireland, where consumers are grappling with a housing market collapse, was £1.25bn, just 49mn pounds better than in the first quarter.Britain is currently sitting on a loss of some £20bn on its RBS investment.Earnings at RBS were also undermined by an £850mn provision to cover the costs of compensating customers who had been mis-sold payment protection insurance.RBS group income in the second quarter fell 5% versus a year earlier to just under £7.8bn as the bank pointed to a drop in revenue at its GBM investment banking operations, citing heightened risk aversion among clients.Hester warned RBS could cut some 2,000 jobs at the GBM division over the coming year. RBS has axed 27,500 jobs, including thousands of investment bankers, and has scaled back its GBM business, reducing its client base to 5,000 from 26,000 and exiting 12 countries.