Discussed this series with a policeman I know. He's loving it because some of the situations encountered are pretty much what fills out a lot of his time.
The mental stress is certainly something that is common. Corruption however black or many shades of gray can also be found.
To the series itself; I was more than pleasantly surprised. Have previously thought Martin Freeman always acted the same way in all the parts I have seen him play, he has now persuaded me otherwise and long may it continue.
I watched the 1st episode immediately after watching Trigger Point. Thought the difference in quality was stark. Trigger Point was a big disappointment but the evening was saved by Responder. Have since blitzed it all and sincerely hope a 2nd series is commissioned - if only to cheese off Alan Sugar.