THIS week, I had an unexpected opportunity to revisit an old friend. My theatre tour has taken me to Cardiff, where Doctor Who is filmed.

By chance they were night filming just round the corner from the theatre at which I am appearing and invited me to pop in and see what was going on. How could I resist?

I must confess to a certain trepidation. I went back to my old school a couple of years ago and discovered it to be a strange and unsettling.

Things seemed the same but were different. Or perhaps I had changed and the place hadn't? And there was no one there whom I knew, of course.

However, returning to a night shoot on Doctor Who was reassuringly familiar.

The personnel had changed certainly, but the atmosphere hadn't.

I had worked with David Tennant before he became the Doctor and therefore knew him.

He came and chatted between takes for what looks as if it is going to be yet another superb Christmas special.

I also got to meet his companion for this story - Kylie Minogue who was relishing the opportunity to demonstrate her acting prowess on television again.

I loathe spoilers of any kind, so will not elaborate on the detail of the story.

What was reassuring for this old Tardis keyholder was that although the programme has moved into the 21st century and manages that impossible task of appealing to a completely new audience without losing the beating heart of the programme, the process and the atmosphere on set remained as special as I remembered it.

I can think of no other job I have done which would see me at 3.50 in the morning still enjoying the work in the company of others similarly motivated.

What was particularly unexpected was the welcome that Russell T Davies and Phil Collinson, respectively executive producer and producer, afforded me and the very genuine affection they appeared to have for the original programme - "Classic Who" as it is now called.

I must confess to a moment of quiet envy seeing David, impeccable in a tuxedo, surrounded by bizarre aliens doing his time lord thing.

It brought back happy memories and it was uplifting to be, for a moment, part of something that meant a lot to me and now means a whole lot more to a new generation of television viewers.

Long may it continue to do so.