INVESTIGATORS from Britain's Serious Fraud Office (SFO) will travel to Japan this week as part of an enquiry into whether a former Sumitomo copper dealer acted alone in amassing $1.8 billion (£1.1 billion) losses in unauthorised trading.

They want to interview Sumitomo officials and Japanese authorities. The SFO did not say whether they would also meet the rogue trader himself, Mr Yasuo Hamanaka. Some reports suggest that losses could more than double to 54 billion.

The SFO's inquiry is part of an international effort to establish whether Mr Hamanaka was acting alone in trying to rig copper prices or whether there was a web of malpractice.