
A stowaway is a person who secretly boards a vehicle, such as an aircraft, bus, ship, cargo truck or train.To travel without paying and without being detected. The young man might be one of the guys who clean the aircraft and probably he found a way to enter into a hidden place. He would have come out from the place where he hid himself when the flight landed in London. Probably further delay caught him unaware as the same flight returned back to Lagos with passengers from London.