TV tonight: Vanessa Williams sits for this wonderful portrait competition

She joins Lennie James and Sheridan Smith on Sky’s Portrait Artist of the Year. Plus: reaching the bottom of Britain’s deepest cave. Here’s what to watch this evening

8pm, Sky Arts Stressful or soothing? It’s always a fine line between the two with this portrait competition. Art historian Katy Hessel joins the judging team for the show’s 13th series, with Stephen Mangan resuming hosting duties. The first three sitters are actors Lennie James, Sheridan Smith and Vanessa Williams. Who will break down in (happy) tears, telling a painter: “You’ve captured something I thought I’d lost”? Hollie Richardson

8pm, BBC Four Titan is the deepest cave shaft ever found in Britain. A gutsy scanning team head in there in an attempt to find out exactly how large it is, and it might even be too big for them to manage. The programme also looks at other cave discoveries, including the 17th-century “witches’ marks” at Creswell Crags. HR

9pm, ITV1 Richard Armitage probes corpses for clues as maverick Bristol pathologist Dr Ethan Winter, a man troubled by the murder of his fiancee and by the similarity of this show’s premise to countless others. As a brutal murder proves not to be all it seems, Winter’s hunt for the truth gets risky. Jack Seale

9pm, Channel 4 Living in an old driving test centre felt like a good idea when Edinburgh artists Jana and Rory first had the opportunity. But the freezing winters have tempered their enthusiasm. Can they turn the site into a modern home on a limited budget? And can their kids live in a caravan while they try? Phil Harrison

9pm, Channel 5 A sad and shocking look at the unexpected death of 16-year-old Danny Nicholls, who was found unresponsive on the living room floor by his sister. A medical investigation showed a hidden reason that could have suddenly stopped his heart from beating. HR

10pm, Channel 4 From Greenock to Vegas, baby! Line of Duty’s Martin Compston relocated to America’s playground when he married a local. In this episode, he brings his Tom Cruise-like glee to pole dancing, flying in a helicopter across the strip and meeting the “king of Vegas”, singer Wayne Newton, who at 84 is still going strong. Priya Elan