Speaking to the Evening Standard, commuter David Banks said: "There were just a lot of police around, police vans and cars and officers around a skip. The skip was between one of the exits to the railway station and car park itself."
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John Cantlie, who worked for a number of Fleet Street newspapers, is thought to have been taken hostage in November 2012.
The union published a 'no show' league table for last year the worst offenders for cancellations.
Zalkalns was jailed in his native Latvia for eight years in 1988 after he admitted killing his wife with a piece of electrical equipment.