Spiral (BBC Four, 9pm & 10pm)

THE eighth and final season of the French drama continues. Gilou is offered a way out of jail if he agrees to become an informer, but on the condition that he keeps away from Laure.Meanwhile, the police team focus their investigation on the Paris neighbourhood of Barbes, where vulnerable delinquent minors are being exploited by receivers of stolen goods.  Then, in the second half of tonight’s double bill, the police investigation screeches to a sudden halt, and Gilou gets himself hired as a bouncer in Cisco’s nightclub and gets to know the security manager Cisco’s son, Titi.

The Masked Singer (STV, 7pm)

The oddly compelling singing contest continues as five celebrities put on their elaborate costumes and prepare to belt out a number.  As ever, panellists Rita Ora, Jonathan Ross, Davina McCall and Mo Gilligan have the job of trying to work out who is hidden beneath the disguises – and, sadly, they won’t be able to hear the viewers shouting out their best guesses at home.  Luckily, to help ease some of the suspense, a third celeb will be unmasked tonight as they leave the show.

Secrets of the Royal Palaces (Channel 5, 8.30pm)

Tonight, we explore Balmoral, built by Prince Albert as a Highland getaway for himself and Queen Victoria.  Part medieval fortress, part French chateau, it’s not to everyone’s taste, architecturally.  But its function today is just as Prince Albert intended: to provide the royal family with a retreat from prying eyes.  We also hear the story of how renowned portraitist Lucian Freud painted the Queen and how, four years after the death of Princess Diana, police made a dawn raid on the house of her ex-butler Paul Burrell and found more than 2000 items of her clothing and possessions.

Paul Sinha’s TV Showdown (STV, 10pm)

Usually, Paul Sinha is the man answering the questions – he found fame as one of the resident experts on The Chase and has also recently appeared on the primetime spin-off Beat the Chasers.  Now, though, he’s going to be asking them as he hosts this brand-new TV-themed comedy quiz show. It should definitely play to Sinha’s strengths. As well as being an expert on telly trivia, he also has a background as a stand-up. But, while the contestants may be used to appearing on the small screen, how much do they actually know about it?  We’ll soon find out as team captains Fay Ripley and Rob Beckett are joined by celebrity guests Denise van Outen, Adil Ray, Catherine Tyldesley and Josh Widdicombe.