I think Rabbett Rover may have asked me about this when we conversing on the website aronline a while back in relation to a pre-production Rover 75 that had appeared a Car of the Month, and I had not got back to him. Rabbett Rover - my user name started as "David" and I seen to recall you were listed as Lewis.
I certainly do remember this episode featuring the Rover and Jaguar - the character Jerry Standing had plied the driver with plenty of alcohol in a bar to the point where he was over the limit. He then allowed him to drive off in his Jaguar XJ8 before phoning the uniformed officers. This was a 'legitimate' way of getting finger prints and DNA from him once he had been arrested.
I believe the episode might have been "Good Work Rewarded" which was episode 5 in Series 1, first broadcast in April 2004. It was based around the murder of a young boy on a golf course.
The following link might be of further help:
http://uk.ask.com/wiki/List_of_New_Tricks_episodes
If I am right based on my powers of useless information retrieval, please don't call me Brian Lane!