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.
More top news
His Royal Highness rounded off his visit to the region by giving a speech at Virgin Money headquarters in Newcastle.
Sunshine and showers tomorrow - but it is the calm before the storm.
Prince Harry joined Steve Cram and Jonathan Edwards in training those taking part in the London Marathon for charity Heads Together.