I really enjoyed Dangerous Knowledge from Southern Television. Some fine acting and effective direction give this a real `thriller edge', and the fine cast are deployed to good effect. For a mid-1970s TV drama, produced by a small regional ITV company, this has real quality; plenty of location filming, aerial sequences, car chases and a couple of shoot-outs. Some reviewers have criticised the plot, but I think it stands-up well (and all thrillers have plot holes to some extent), and it should be remembered that it was originally designed to be seen in weekly instalments, so watching it back-to-back is bound to shift our perspective on plausibility.
John Gregson and Patrick Allen were particularly good, but the whole cast was excellent - a special mention to Elisabeth Bergner, who gives a really believable performance as ex-spy Madame Lafois. A special mention too for the cracking theme music by Christopher Gunning - has to be up there with his best work, and it's a great shame that it's not better known; Gunning doesn't even mention it on his list of TV music credits on his website.
Oh, and finally, one reviewer states that Southern produced this as part of the ITV anthology strand Armchair Thriller, but this is not the case - it was a stand-alone drama from Southern Television that was networked.