To me this was the best episode of the first series. The reason being if you stripped this episode down to its basic elements, you would find that is was simply a Lovejoy versus Gimbert episode. And nothing can be finer than seeing these two be at log heads with each other. The famous Gimbert line "Since my wife's death, I needed someone to hate" perfectly describes the relationship of the two. It is not of pure loathing, but more of one up men ship, trying to get one over the other (similar to Del-Boy and Boycie in Only Fools and horses). And this episode emphasised it.
The episode itself was small and self-contained and had little action compared to the rest of the episodes in the first series, and to me that was a good thing. You had a chance to see recurring characters (such as Dandy Jack and Helen) becoming more integral to the show and for the first time we get to see Lovejoy's daughter (who in my opinion is my favourite out the of the three), so with this self-contained episode, you can really feel the sense of a community and again to me that was a good thing. The sting itself was beautifully played and it also gave us insight it the principles of forgery or copyist (if you're not caught)
My favourite moment in this episode was the scene with Lovejoy and Gimbert discussing their relationship in the field when Gimbert is clay-shooting.