the father of one of three teenagers arrested in turkey on suspicion of trying to join islamic state fighters in syria works for the ministry of defence , it has been revealed .
it is believed the man , from brent , northwest london , works in the military 's post office , where he could have had access to the names and address of all military personnel at home and overseas .
he has been put on compassionate leave from his post , after the mod considered suspending him , a source has said .
it was revealed that the students were intercepted in turkey after their parents realised they had fled to join the terrorist group .