Scotland Yard says it is "too early to speculate" on Russian reports that the attack could be a gangland hit linked to a murder attempt on another banker, Alexander Antonov, in Moscow.
The force's Trident command - which investigates gang shootings - is understood to have liaised with overseas counterparts in the hunt for the gunman behind the attack on Tuesday evening.
More top news
The number of night workers has risen to three million since the recession, with more women than ever working antisocial hours.
Sixteen Colombian police officers have been killed after their helicopter crashed while searching for the nation's most-wanted drug lord.
Two men have been arrested after a methamphetamine lab was discovered inside a Taco Bell restaurant in the US.