“Blink and you’re dead. Don’t turn your back. Don’t look away. And don’t blink. Good Luck.”

Keeping that cheerful advice from David Tennant in mind, I’m ready to eyeball a strong candidate for the scariest character in the whole 48 years of Doctor Who.

The statues outside one of the Cardiff University buildings, were some of the many in the city filmed as Weeping Angels in the 2007 episode “Blink”. Break unwavering contact with these cold stone eyes for a millisecond and they come to life, rip out your brains and reanimate your mind.

Phew, survived that. Now I can face the lingering aura of terrifying Cybermen,  Sontarans, Slitheen, Clockwork Droids – and of course Daleks – in any Doctor Who location anywhere in the Welsh capital with confidence.

Time for some light relief.  Helen, our guide from Brit Movie Tours leads us through the Saturday shopping throng  to the site of some typical Time Lord mayhem.

We stop outside the cash machine at Waterstones.  This is where the Doctor, in The Runaway Bride, creates a diversion by making £10 notes flutter out into the Cardiff breeze,. Instead of the Queen, they bore Tennant’s  head, and the promise “to pay the bearer on demand the sum of 10 satsumas.” Some of the delighted passers-by that day still have them.

Cardiff used to be a  regular sort of place, with its  huge city centre castle,  a very fine museum and art gallery, several stately shopping arcades and a bustling  new retail centre to which they just added one of the biggest John Lewis stores in Britain.

That all changed when scriptwriter Russell T. Davies, as t happens from the city’s big rival Swansea just down the M4, revived a defunct TV series, off our screens for 15 years. BBC Wales was given the job of making Doctor Who.

Since 2005 the Doctor,  and his spin-off colleagues in Torchwood  and Sarah Jane, have been weaving in and out of the space-time continuum like fly halves at that nearby city centre temple to rugby, the  Millennium Stadium.

Images of the city (even if they are apt to fuse with bits of London, as when the city’s St Mary Street suddenly becomes Oxford Street) are fixed  in the subconscious of millions around the world – there are people on our tour from Australia, Canada and…Swansea,.

We follow Helen into the cool and calm of  St John’s Church.

“So what happened here,”  Helen asks the group. Engaging light-speed mental overdrive, a serious fan in a checked shirt zips back the answer.

“Yes, it’s Catherine Tate’s first episode, as Donna, where she walks down the aisle to get married but takes off and heads for the TARDIS.” Dramatically it’s up there with the wedding scene in Lorna Doone.

Next stop is the pavement outside one of the best-known department stores in South Wales, Howells. It stands in for Henrik’s in Oxford Street, where Rose, Billie Piper’s character works. The scene where it  “blows up” and crazed mannequins go on the rampage down St Mary Street  has entered local folklore.

With the keen eye of tireless sleuths, BBC location scouts have probed every corner of Cardiff, and points across  South Wales – for the right setting, although there are many  that even the locals  won’t recognise . In the magnificent Millennium Stadium in the heart of the city, for example, action scenes take place deep inside,  well away from the pitch. “if there’s a corridor scene, they properly shot it there,” says Helen.

We  board a coach  for the trip down to  what used to be Shirley Bassey’s famously rough and edgy Tiger Bay, where they honour the memory of another famous storyteller.

The centrepiece of the bright new Cardiff Bay development is the

big European-style plaza, Roald Dahl Plass. (It celebrates the writer’s  Welsh, and Norwegian, lineage.)  On one side is the towering slate and metal-clad Millennium Centre. it has starred in the series  as the Musee d’Orsay,  and a hospital in  a far-in-the-future New York.

Directly outside is a 70 feet high stainless steel obelisk, sheathed in a permanent waterfall. This is one of the most important junctions in  the universe, at least  as Dr Who and Torchwood scriptwriters see it. Below it  is  the entrance to the “Cardiff Rift”, a  “wormhole” with its other end floating through and space and time. The scary Gelth, blue gaseous life-forms, have the habit of appearing down it.

Right on cue fantasy invades reality and the entire group go missing as I have my photograph taken. I briefly imagine them hurtling through the universe somewhere, and wonder if a call to Capt Jack Harkness is in order.  Then they all reappear with ice creams.

We head west down the Butetown Tunnel, under the River Taff, watching sequences from the relevant episodes . The keen-eyed have already spotted this as the place where the London bus takes off in Planet of the Dead, and flies away to the desert world of San Helios, aka Dubai.

As we head out of town, Helen hands out more refreshment, in the form of gingerbread Doctor Whos, which she made herself.  At the moment Sylvester McCoy seems to be most popular, closely followed  (among the ladies) by Matt Smith, possibly because she didn’t have enough icing to give him clothes. Sad to say there don’t seem to be many takers for good old William Hartnell.

One of the reasons Doctor Who is so well-liked is the range of the stories. Full-on intergalactic war may not be your cup of tea, but what about the gentle romance of the episode Human Nature, where David Tennant’s Doctor, relinquishes his role and  becomes  plain John Smith,  a village  schoolteacher  in 1913?

We are outside Gwalia Stores, at the Museum of Welsh Life in St Fagans  six miles from Cardiff. It’s a real 1880s village shop, moved here to a stone by stone from Ogmore Vale. This is where the teacher/Doctor’s superpowers kick in just as a passing mother and child  are about to be squished by a falling piano. He averts disaster In a microsecond,  hurling a cricket ball to make a dozen consequential things happen.

Our final call is Llandaff Cathedral,  the location  for another favourite, the gentle story of Vincent van Gogh from the 2010 series, with Matt Smith as Doctor Who.  The Cathedral stands in for the Church at Auvers, subject of one of the artist’s best known works.

Helen, as a bonus, stages a mini drama. Using the original script, she plays Amy Pond furiously berating the doctor, (played by the man in the checked shirt)  for staying away 12 years when he said he would only be gone five minutes. That episode was shot here too, in the fictional village Leadworth, an anagram of  “Doctor Who late.”

Back in Cardiff, we pull up outside the University again.  They used the Glamorgan Building as Churchill’s War Rooms.  This is where the Matt Smith Doctor meets his nemesis, now working for the war effort, in oddly quiescent mood. The Dalek delivers, for me, one of the immortal Doctor Who lines: “[to The Doctor] Would you care for some tea?”

The Doctor Who Location Tour is run by

Brit Movie Tours

0844 2471 007

The writer travelled courtesy of First  Great Western  www.firstgreatwestern.co.uk, 08457 000 125