Here's an idea. Why don't SAA try a last minute change of destination from London to...ooh I don't know...let's say Singapore. In other words the crew who were supposed to fly to London now all of a sudden find themselves going to a place where smuggling drugs mean the death sentence. Not that it ever will (or should!) happen. As a passenger one would feel slightly uneasy of taking a flight where the only one who doesn't know the destination is also the one supposed to take you there!
Failing anything that drastic why don't they tighten up the security arrangements? It used to be that airport security was the responsibility of the Police Force (used to be called SA Railway Police) - not a private contractor in sight. How can they expect proper security when they employ people at minimum wage, make them work a minimum of 60 to 72 hours per week (which is the only way the poor guy can earn enough money to survive), tax him to death on any overtime, and to top it all expect him to be happy doing that for the rest of his working life? No chance of advancement because as far as his bosses are concerned he's just there to provide a bum on a seat. No quarterly performance reviews, no opportunity for him to attend courses, and have you tried studying anything when you work 72 hours per week at some mind-numbingly boring job? From leaving his house to returning at the end of a day your man probably has a 16 hour day what with travelling on trains etc in SA.
Is it any wonder that he'll look the other way when some criminal offers him probably close on a year's wages just to let one or two cases go past unchallenged? Especially when said criminal is living the high life, driving a nice car living in a nice house etc etc etc.
Until they address this at the root it will never change.