Some top JPMorgan Chase & Co. executives and directors were alerted to risky practices by a team of London-based traders two years before that group's botched bets cost the bank more than $2 billion, the Wall Street Journal reported today. 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 would not be allowed to go overboard in the future. Last year, top CIO executives set a plan to roll back a separate set of large London trades—only to learn later that the plan had not been followed correctly. The concerns dating back to 2010 show that JPMorgan had an opportunity to avoid the bungled trades, which over time could cost the bank as much as $5 billion.