Silent Witness (BBC1, 9pm)

SILENT Witness returns to celebrate its 20th anniversary this month, featuring five new contemporary stories that start among the familiar landscapes of London and end up in the dusty scrubland of Mexico.

Tonight, in the first of a two-parter, the body of 20-year-old Lorna Katz is discovered drifting in the River Lea, with evidence suggesting she was tied up somewhere before she floated downstream. However, the death takes on an ever-more sinister significance when the team discovers that Lorna was the best friend of Ruth Tresize, a teenager who disappeared three years previously, with the missing girl's mother Ali becoming fixated on Nikki for information, convinced that the two incidents are connected.

Having started as Dr Nikki Alexander, back in 2004, what does actress Emilia Fox feel about having reached a decade as the medical examiner?

"I feel hugely privileged to still be a part of it. The regular cast has gone through various transformations, but the heart of Silent Witness remains the same: it's primarily about solving crimes where the clues are found within the dead bodies, and the importance of forensic science and pathology to understanding the last ten minutes of someone's life. The programme has to keep up with advances in technology and forensic science, and as the technology of film-making advances I have seen many changes in that too.

Over the years everyone involved has aimed to keep production values high and social media has helped to gauge how the fantastically loyal audience feel about the show and what they want from it – and it has brought a new audience to it too.

Milestones in the series involve finding out more about Clarissa's (Liz Carr) personal life and in the final episode Jack and Nikki find themselves in Mexico, where they are helping to identify the remains of victims of cartel violence.

"It's an extreme situation and it was without doubt the most challenging episode I have ever worked on, but I think it will be hugely surprising for the audience which is thrilling. It was challenging both for me and for Nikki. I have never filmed an episode like it, nor have I ever done the things I had to do in it on anything else. It was hugely emotional, physically demanding and quite an experience! I am so proud of Silent Witness for being a show that can continue producing new and surprising episodes like this one," says Fox.

"I think good, ambitious writing is key to the series' success. I love how writers find different themes and ways of exploring what happens in the crime-solving process. I hope people enjoy the regular characters too, and the different worlds they get taken into depending on the circumstances and where the bodies are found. The two-hour format is very useful as it allows the audience to get to know the guest characters, and the fact the story is told over consecutive nights means you don't have to wait too long for the conclusion, which has been a good thing for Silent Witness."

Trump: The Kremlin Candidate? – Panorama (BBC1, 8.30pm)

IN the week of the new President's inauguration, Panorama investigates Donald Trump's relationship with Vladimir Putin. John Sweeney – who has confronted both men in the past – travels to Russia, the United States and the battlefields in Ukraine to report on what's behind their mutual admiration. He examines whether Russian cyber-warriors helped get Donald Trump into the White House and asks how safe the world will be if they stay friends – or if their relationship falls apart.

The Halcyon (ITV, 9pm)

IN the wake of the fall of France to the Germans, guests flood into the hotel, including one who catches Lady Hamilton's eye – the Comte de St Claire. Peggy worries about Billy's enthusiasm to sign up as soon as he turns 18, but knows there is little she can do to protect him when his mind looks like it's made up to join his father's regiment, infamously used as cannon fodder. Viv Hardwick