Britain's top police officer on Friday said an investigation into how a terror suspect escaped from prison would look at whether he had help.
Former soldier Daniel Abed Khalife, 21, is believed to have strapped himself to the underside of a delivery van to flee Wandsworth prison on Wednesday.
His disappearance has sparked a nationwide manhunt and an all-ports alert to prevent him from leaving the country.
On Friday morning, Metropolitan Police Commissioner Mark Rowley said the hunt was focused on sprawling Richmond Park, near Wandsworth, in south London.
He told LBC radio in an interview that the escape was "clearly pre-planned".
"The fact he could strap himself onto the bottom of the wagon, I mean, there's obviously some logistics involved inside," he said.
"Just to work out a prison escape and how you can do the logistics of it and get the right equipment and how you're going to do it is unlikely to be something you do on the spur of the moment."
Khalife's escape has prompted wider questions about security at UK prisons, which staff say have been hit by under-funding and personnel shortages.
Asked if it might have been an "inside job", Rowley said:
"We're going to have a look at everything as part of this investigation."
Khalife was awaiting trial over two incidents at the Royal Air Force (RAF) base in Stafford, central England, near the army barracks where he lived.
He was accused of "attempting to elicit information of a kind likely to be useful to a person committing or preparing an act of terrorism" in August 2021.
He was also charged with a bomb hoax by placing a suspect device at the RAF base on January 2 this year. He was discharged from the army in May.