Two Daily Mirror journalists who tried to plant a fake bomb on a train have been arrested.
The newspaper reporters were caught carrying their “bomb” by railway staff, who asked what they were doing and then called police.
The two men were detained at Stonebridge Park depot, which is towards the northern end of the Bakerloo Line in north-west London.
The Mirror said they were testing out security in a “legitimate and justified journalistic exercise” after managing to plant a fake bomb on a nuclear train last year.
A spokesman said the latest attempt was in the interests of public safety and “we are happy to see that the security procedures have now improved.”
British Transport Police said the men had been arrested at the depot on suspicion of trespass.
Officers were still searching the depot and the men have not yet been charged with any offence, a spokeswoman added.
In January, a Mirror journalist planted a fake bomb on an unguarded train at Didcot Parkway Station in January.
It sparked an urgent review of security arrangements for Defence Ministry trains.
Six months earlier, the paper ran a similar expose involving trains carrying nuclear waste to Sellafield.
That report involved a journalist called Tom Parry, who is believed to be one of the men arrested in the latest incident.