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
A medical tribunal found Dr Mark Bonar posed a "potential future risk of harm to patients".
After a lively start to the long weekend with torrential, thundery downpours - a drier night.
The bouncy castle, commissioned for the Common People festival, is taller than the Great Wall of China.