Police who found the three boys who went missing four days ago said there may have been a plan to "spirit them out of the country."
They failed to return to their foster carers' home in Sunderland, after setting out on a tea-time bike ride to a local park.
Instead, they caught a Metro to Newcastle, then took a pre-booked taxi to London and spent two nights in the capital before heading for Birmingham.
Superintendent Alan Veitch, who led the major investigation to find them, said it was "entirely possible" that the plan was to get the boys out of the country.
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The constituency of Washington and Sunderland West includes the UK's largest car plant, which was opened by Nissan in 1984.
This seat was formed prior to the 2010 General Election, taking in Sunderland city centre and the Ryhope area to the south.
The constituency of Stockton South includes relatively affluent areas like Yarm and Eaglescliffe.