Oh my.. Too hard. Like I put in the review at amazon.com for the US DVD version of series 5, both 5 and 6 are what I consider the best of the early seasons when the show got its legs and really shot off. Two favorites of mine on here along with other very good episodes.
After doing Eenie Meenie.. and then going through the alphabet with the two choices. I picked In the Service of Humanity.
Odd Dog Men was the second choice. Maybe it was timing (Brian Wilde's death when it aired here), definitely his speech going on about becoming an O.B.E. for dog-walking, but this was such a great episode.