Lewis: Reputation, which aired on Sunday night on ITV, showed once again that detective-show formulas are often a bigger draw than the detectives themselves. Just as Taggart outlived Taggart himself and Rebus is going strong despite the replacement of John Hannah by Ken Stott, so Inspector Morse seems to be able to go on even though Morse has passed the investigating torch on to his former stumbling foil Lewis.

Reputation was pretty much by-the-book TV Morse. In fact, it was concentrated Morse, with more Latin and Hamlet per square inch than any previous Morse mystery – as though the producers were trying to assuage any fears that the Philistine Lewis would take things downmarket.

As per usual, various academics and students were either murdering or being murdered. For two, very long hours, Lewis proceeded to stumble cluelessly around Oxford, no doubt with the kind cooperation of the Oxford Tourist Board, which must have been desperate for some new Morse to bring some interest to the town again. Like a Knights Templar conspiracy theorist, at no point did he use any investigative technique that remotely resembled actual police methods, preferring instead to search for answers in crossword puzzles and mottos. Again, so far, so old-school Morse.

Nevertheless, it was clear that the old Morse production team weren't simply going to cross out His name in the titles, replace it with 'Lewis', and hope nobody noticed. Lewis remained resolutely the same character as before, despite his promotion, with the requisite erudition being passed on instead to former theology student turned police officer, DS James Hathaway. They made for an interesting team, with Hathaway essentially getting the really bright ideas but Lewis having the experience and wider knowledge to know what to do with them - a subtle shift in the Morse-Lewis dynamic. However, Laurence Fox (son of James, cousin of Emilia) followed in his father's footsteps by playing Hathaway as rather a stiff individual, even in his lighter moments, leaving Lewis as the 'heart' of the central crime-fighting duo once again.

The final revelation of the murderer came as no surprise to anyone familiar with the Columbo school of whodunnits, although said murderer's motivation for his crimes made so little sense, you knew in an instant you were still watching classic Morse in action. The names may change but the structure stays the same.

With astonishing ratings of 11.3 million, Lewis will undoubtedly be making a return to our screens in the near future, barring equally astonishing incompetence or bad luck. That means Morse fans can finally relax in the knowledge that the proven formula of a couple of murders, Oxford scenery and some posh people getting their comeuppance over the course of two interminable hours will be theirs to enjoy again. After all, just as a crossword is a crossword is a crossword, so a Morse mystery remains the same, whether you call it Lewis or not.