The cast and crew of hit TV drama Lewis were joined by a very special extra as they returned to the scene of many a famous Morse investigation.

Filming of episode four of the programme's third series, they used the Randolph Hotel, in Oxford's Beaumont Street, as the backdrop to a storyline that featured a cameo from Colin Dexter, whose novels created the famous characters.

The author joined stars Kevin Whately and Laurence Fox to film a brief walk-on role — a habit he was renowned for in the original Morse episodes. Mr Dexter, 78, said: "I'm with the stars today, or maybe I should be putting it the other way around — the stars are with me.

"Each of them has promised to underplay their own parts, and I usually try to lift my performance. In the finished film I would imagine I will be on screen for a subliminal second. If you add all my appearances together I'm sure it would stretch to two or three minutes.

"It's enough time to show your versatility. I've played the high life and the low life, from the Bishop of Oxford to a tramp. I did once have a speaking part as the Bishop of Oxford and that was wonderful."

Mr Whately, who plays the title role, joked: "It is in my contract that Colin can't appear behind me in my scenes. It's fine if he upstages Laurence.

"We only let Colin speak in Latin or Greek, so no-one knows he's overacting like crazy. He probably has enough screen time for a show reel. His performance as a tramp was probably his finest moment."

The Geordie actor added: "It's great to be back at the Randolph. We have probably had five or six episodes (of Morse) filmed here and one early on — I think in the second year — set almost entirely around the hotel.

"That was the Wolvercote Tongue, which had Simon Callow in it, and it just so happens that he is in this new one as well."

Mr Dexter said: "I would think we have been here far more times than any other location."

Filming was expected to last all day, although Mr Fox, who plays Det Sgt James Hathaway and became a father with wife Billie Piper last week, caused a brief hold-up as he burned his socks while keeping warm in front of the Randolph's open fire.

Lewis fan Gruff Humphreys, from north Wales, was one of a number of people watching the action unfold outside the hotel. He said: "I'm down here on business and it's a lovely surprise to stumble across the filming. I used to watch Morse religiously and I've really enjoyed Lewis."