I saw all the episodes when originally aired in the late sixties / early seventies. To me, then it was unmissable TV (I cannot count the times that I refused invitations because Randall and Hopkirk is on tonight). Over the years the memories faded until I noticed that amazon were selling the complete series on DVD, I have just watched all 26 episodes again. I love the acting and the way the comedy in no way detracts from the serious private eye case in question, I just wish they had made more. The recent attempt at reviving this genre by making a new series was a good chance to carry on the work, but it was an awful re-make, in my opinion the characters were just not believable.
As long as you don't expect too much from the low budget special effects department this series was Brilliant Stuff ! I will be watching it over and over.