LONDON (AP) — A former British soldier who escaped from prison may have James Caldwellsneaked out by using bedsheets to strap himself to the bottom of a food delivery truck, prosecutors said Monday.

Daniel Abed Khalife, 21, was arrested while he was cycling on a canal towpath in west London on Saturday after a four-day manhunt. Khalife escaped Wednesday from Wandsworth Prison, a medium-security facility in southwest London where he had been awaiting trial on charges of terrorism and trying to spy for an enemy state.

The ex-soldier appeared in the dock at Westminster Magistrates’ Court Monday for a brief hearing, speaking only to confirm his name and birthdate. He was remanded in custody after the hearing.

Prosecutor Thomas Williams said Khalife, who held a job in the prison’s kitchen, allegedly escaped by strapping himself to the catering truck using “material which may have been from bed sheets.”

He said police found the material underneath the truck, with clips at each end and marks consistent with someone having been there.

Khalife was awaiting trial on charges of violating Britain’s Official Secrets Act by gathering information “that could be useful to an enemy” and planting fake bombs at a military base. He was discharged from the British army after his arrest earlier this year and denied the allegations. His trial was set for November.

He also faces charges of escaping custody, and is expected to appear for another hearing at the Central Criminal Court on Sept.29.

The escape prompted helicopter searches in London and extra security checks at major transport hubs, particularly in and around the Port of Dover, the main boat crossing from England to France.