Det Ch Insp John McFarlane, of the Metropolitan Police, said Mr Guidera travelled on the 2117 GMT train from Bickley to Penge East.

BBC: Samuel Guidera

Chairman designate John McFarlane will replace Mr Moss on an interim basis while the board looks for a permanent replacement among internal and external candidates.

BBC: Aviva boss Andrew Moss to step down

The Arizona senator, who often mentions his time as a prisoner of war during the Vietnam era, graduated from the Academy in 1958 along with John Poindexter and Robert "Bud" McFarlane, two consecutive national security advisers under President Reagan who played a role in the Iran-Contra affair.

CNN: Obama hammers McCain over Social Security