A fantastic effort set in the mid 70s when East/West tensions were running pretty hot; the Cold War was a very real experience for those such a myself, then serving in the British Army. Whilst I never served in Berlin I did visit and it was absolutely chilling to see the "Anti Fascist Barrier" - all that effort just to keep their own people in.
I appreciated the great attention to detail re the (presumably CGI?) rendition of the Teufelsburg - we just referred to it as "The Hill" ditto the views of the Wall. Sadly, the same attention was not applied when it came to uniform details and equipment; perhaps as an ex-soldier I would say that but to see all that effort put into the scenes above, the civilian vehicles and the fashions of the time, and then to compromise it all with a Second World War jeep at Checkpoint Charlie, Gulf War medal ribbons on RAF officers' uniforms, and risible portrayals, albeit in the background, of British servicemen's attire was at times unforgiveable.
All that effort and you then mess it up because, presumably, you just couldn't be bothered to go the extra mile; a shame, because the plot worked well, and the overwhelming intrusion of the State - as portrayed in the East - was overpoweringly sinister.
Overall, a good effort and there should be more thrillers covering the Cold War, but if there's a next time, and you need to get the military details right, give me a call; I'll do it for free.