The head of oil and gas research at Ambrian Partners has left after only five months in the role, dealing a blow to the natural resources-focused brokerage that had opted to return to its core business in a year described as “the hardest that many UK stockbrokers have ever seen”.

Simon Hawkins is leaving Ambrian to become head of global energy research at US money market and commodities trader MF Global, according to a source familiar with the move.