A MAJOR hunt was in progress last night after a laptop crammed with secret data was stolen from inside the Ministry of Defence nerve centre.
The machine, plus an encryption key to unlock highly sensitive files, vanished from the heart of the MoD's London HQ.
It sparked fears that a "mole" is operating there.
Last night a source said: "This has the potential to become one of the most serious security breaches at the Ministry for a very long time.
"Laptops have been mislaid before, but not with encryption keys."
The computer was left in the HQ by a high-ranking RAF officer.