Britain's state-rescued Royal Bank of Scotland issued a warning over future earnings despite posting a surge in profits on Friday.
Net profit almost tripled to £1.425 billion ($2.42 billion, 1.8 billion euros) in the six months to the end of June, compared with the outcome equivalent period in 2013, the bank said.
Pre-tax profits jumped 93 percent to £2.65 billion, it added.
"These results show that underneath all the noise and huge restructuring of recent years, RBS is a fundamentally stronger bank that can deliver good results for customers and shareholders," said chief executive Ross McEwan.
"But let me sound a note of caution. We are actively managing down a slate of significant legacy issues.
"This includes significant conduct and litigation issues that will likely hit our profits going forward. I am pleased we have had two good quarters, but no one should get ahead of themselves here -- there are bumps in the road ahead of us."
The Edinburgh-based bank is 81-percent state-owned after it was rescued with £45.5 billion of British taxpayers' cash during the 2008 global financial crisis, making it the world's biggest-ever banking bailout.