Royal Bank of Scotland has swung to a loss in the third quarter after taking a hit from the cost of payment protection insurance. The Edinburgh-based bank, in which the government owns a 62% stake, added its investment bank had a "particularly challenging" three months. It reported a pre-tax loss of £8m for the July-to-September period after it took a £900m charge for PPI. These are the last results before chief executive Ross McEwan departs. The New Zealander is being replaced by Alison Rose next month, when she becomes the first woman to lead one of the UK's big four banks. She joined the bank 27 years ago as a graduate trainee. The bank had reported a £961m profit in the same three months a year ago.