Silent Witness stars Emilia Fox and Amanda Burton meet for the very first time

“At the time I used to love wearing petunia and lavender,” remembers Burton, “and I thought, ‘If I take my favourite smell with me, I’ll block out this smell.’ But you can’t do that. Someone said to me: ‘Never wear your favourite perfume when you go in, because you will always associate that smell you love with the smell of a cadaver.’”

They speak with such ease together, it’s incredible to think that before today’s specially convened 20th birthday party Burton and Fox have never met each other. When the baton was handed over early in the eighth series in 2004, there was no crossover, no on or off-screen debrief. It was a clean break, a new start, all round. It wasn’t a competition then and it isn’t, I assure these top-drawer, much-loved actors, one today either.

Burton in Silent Witness

We’re only 20 minutes into this carefully arranged conversation when I read out the first words ever uttered by the debut heroine in a lecture to a bunch of fellow professionals: “Take your time. The body’s going nowhere. Look first, act when you and your colleagues are ready and act together. They say a victim only dies once, but a crime scene can be murdered a thousand times.” And suddenly Burton starts to cry.

The 60-year-old Northern Irishwoman is dabbing her eyes, struggling for words. She may have left the show 12 years ago and been busy ever since (from Lynda La Plante’s The Commander to, back in the autumn, playing a gangster’s wife in ITV’s The Level), but clearly her time on Silent Witness was one of the defining experiences of her career.

“It dominated my whole life…” she begins, speaking of a role she took on at the age of 40. “Sorry, gosh, it’s just brought back so many memories. It’s incredible, really,” she says, composure regained with a couple of sips of tea. “Yes, it was an amazing, amazing show. Really. Still is.”

For Burton, her groundbreaking portrayal came with a side order of pressure. Her no-nonsense Sam Ryan was described by critics as “fearsomely humourless” – mention of which unleashes long bottled-up frustration at adverse comments she feels would never have been levelled at a male.

“They were very hard on me in that show,” she says quietly. “I had a very tough time… When it started, it was incredible, it was so well received. But over the years there was a lot of criticism, which affected me enormously.”

Recalling accepting the part of Nikki Alexander 12 years ago, Fox, 40, says: “I suddenly realised the weight of responsibility, because what Amanda had created was such a following for the series, and a protectiveness, from the people who love Silent Witness. So I said: ‘Please, please don’t make me try and replace Sam Ryan.’ And they said: ‘No, don’t worry, it will be a completely different kind of character. And also, it will be a much more ensemble piece.’ I was more comfortable about that.”

Fox in Silent Witness

Also, to be forensically clear: the actors are not here today because the upcoming 20th series is a Silent Witness: 2.0 reboot, with the super-experienced Professor Ryan and Dr Alexander teaming up to clear up cadaver-based mysteries in record time. That, both agree, “would be a weird thing to do”.

Though fundamentally a crime show, it’s not all child murders, decomposing occultists and Holocaust-survivor horrors. Both agree that Silent Witness has its lighter, more diverting moments. Fox says that the upcoming series required the services of a fly wrangler, “who arrived on set just buzzing with buckets and buckets and buckets of flies. Plus,” she promises, “there’s an animal that I’ve never had on Silent Witness before.” Burton recalls fondly (I think) “some very dodgy sex scenes, ha ha! Really dodgy ones.”

“Nikki doesn’t even get those!” shouts Fox. “Her track record of relationships is absolutely appalling!”

Burton offers up the tale of a memorable interaction with an extra. “There was this man who just really wanted to be on the show and who really liked my character. So he came in as an extra, as a corpse that I was doing an autopsy on. I had an enormous amount of dialogue… and I could see the camera guys, out of the corner of my eye, sort of shoulder shaking. And then I noticed that he had an enormous erection… The crew were killing themselves laughing. Oh, it was awful!” hoots Burton. “Bless him, he was about 70! I was just like, ‘O...K, how about a coffee break?’”

The team: David Caves, Emilia Fox, Richard Lintern and Liz Carr

What, Amanda, do you think your character Sam would make of Nikki? “Oh, that’s an interesting question. She would love her passion, and she would love her tunnel vision.”

And Emilia, what would your character Nikki think of Sam? “I think we’d identify with each other, wouldn’t we?” she replies, gazing fondly at Burton. “Because, to our detriment, the characters are both workaholics, aren’t they? Nikki would absolutely look up to Sam and want to work with her and learn from her, as I do Amanda.”

And then, as the actors share admiring glances and genuine affection, comes the breakthrough that promises a treat for Silent Witness fans (and BBC executives).

“Shall we do a special?” wonders Burton.

“Yes!” Fox shoots back excitedly. A Christmas special next year? “We’d love that! Why not?”

“Well,” smiles Burton, “I think at the end of this interview, you’ve convinced me!”

“And we’re not going to solve the crimes in less time,” Fox insists gamely. “It’s going to take longer, because we also want to do normal things! We want to be able to hang out and talk, like two females would talk when they work together.”

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“We could go on a road trip!” suggests Burton.

“Yes,” Fox nods eagerly. “We’re not just going to deliver information to each other. This would be much more interesting.”

So we’re talking Silent Witness meets Thelma & Louise?

“There we go!” smiles Fox. “That’s it. Brad Pitt, does he come into it?”

Well, obviously. Silent Witness fans, please set your programme reminder now.

Silent Witness is on tonight at 9pm on BBC1