The fate of a number of British hostages held in a desert gas complex remains unknown in the wake of an Algerian military attempt to free them.
They were among foreign nationals held near In Amenas who the Algerian forces attempted to free from militants.
Talking to today presenter Justin Webb, Andy Coward, a chemical engineer who visited the site in 2009, described the security that he had seen as one of the "most secure" of the sites that he had visited.
He explained that there must have been a lot of planning involved: "It was well planned in advance because in terms of getting people to the site you would have to drive a long way... there would be a lot of preparation to get people and munitions ready for that kind of activity,"
Mr Coward described the surrounding desert around the site as "very bleak, very open".
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