Libyan rebels discovered that soldiers captured during a bungled operation were carrying scraps of paper with the usernames and passwords for secret computer systems.
Sources in Benghazi, the largest Libyan city in opposition control, told British newspaper The Sunday Times last week that they seized a cache of communications equipment when the joint MI6 and Special Air Service (SAS) mission went wrong nine days ago - and also found the details needed to access the computers on notes among their captives' belongings.
Several pieces of equipment were even said to have labels saying, "Secret: UK eyes only."
"It is so inept, it is unbelievable," one expert said
After tapping the usernames and passwords into the confiscated computers, the rebels were presented with one screen that read "Sunata deployed," which appeared to preface a program for accessing a secure military network.
"It takes you right into the MoD [Ministry of Defence] system in the UK," a rebel source said, adding that the rebels accessed the network.
"We were, of course, curious. But as a courtesy to the UK, we will not divulge all, but just enough to let them know that we know. It's a good thing this hasn't fallen into enemy hands."
At least eight satellite telephones and shortwave radios, six GPS trackers, five laptops, two satellite internet communication devices and batteries and solar panels to recharge the electronics were found on the troops.
There were also explosives components, maps with color-coded landing and extraction points, multiple passports and several credit cards.
"Some of the communications systems they carried is the stuff that you only see in the movies," said one rebel with military experience, calling the items "espionage equipment."
The seizure of two communications systems was confirmed, but the source claimed that MI6's computer systems were not compromised because the captured computer was "clean".
The MoD also denied that the rebels would be able to access its main network but declined to confirm specifics about equipment used by commando teams.