Some top JP Morgan Chase executives and directors were alerted to risky practises by a team of London-based traders two years before that group's botched bets cost the bank more than $2bn, according to people familiar with the situation.

Interviews with more than a dozen current and former members of the bank's Chief Investment Office, the unit responsible for the losses, indicate that discussions about reining in London traders started as early as 2010. Certain directors were briefed then on a foreign-exchange-options bet that went bad, and were told that the trader responsible wouldn't be allowed to go overboard in the future, one of these people said.