Who Do You Think You Are? (BBC1, 8pm)

GREG Davies’s father made sure that his son was born on Welsh soil so that when Greg became a rugby international, he’d play for Wales.

Fortunately for comedy, Greg showed little talent for rugby; but he retains a sense of connection to his Welsh roots and, two years after his dad’s death, wants to know more about them. Greg gets more than he bargained for when he identifies a wayward great-grandfather, but is rewarded when the trail leads further back to the deepest, Welsh-est roots that anyone could wish for.

Despite his parents living in England at the time Greg was born, his dad insisted that the comedian should come into the world on Welsh soil, and the Inbetweeners and Man Down star has always been fascinated with that part of his heritage.

Trust Me, I'm a Doctor (BBC2, 8pm)

MICHAEL Mosley has been a regular face on the BBC since 1985, though in recent years his appearances on The One Show have made him something of a household name. Shows such as Blood and Guts, and Guts: The Strange and Mysterious World of the Human Stomach, helped boost his profile, but for the past four years this series has really touched a chord with the masses. For newcomers, he and his team provide viewers with evidence behind health claims made in the media. Mosley and the team of doctors return to investigate the best way to keep calories in check – dieting or exercise. Plus, Saleyha Ahsan looks into whether probiotic products can improve health, Chris van Tulleken discovers whether red wine lives up to its healthy reputation, and Gabriel Weston witnesses a sternum implant operation carried out using 3D printing - the first procedure of its kind in the UK.

DIY SOS: The Big Build (BBC1, 9pm)

THERE was a time when the original DIY SOS was just Nick Knowles and a bunch of mates having a laugh as they raced against the clock to transform peoples' houses, and lives. Then the projects became more serious as it became obvious that viewers in floods of tears equalled good ratings. The Big Build continues to pluck at the heart strings with one of the most moving editions to date. Nick, Laurence Llewelyn-Bowen and the team are in the Worcestershire village of Eckington to help 17-year-old Antonia Payne-Cheney. She has a rare condition called Ehlers-Danlos syndrome that causes her joints to regularly dislocate. And because she can't eat normally, she has to be fed through a tube. The builders need to create a sterile space for medical procedures in her bedroom, a specially-adapted wet room and an area where she can socialise with friends and family. Have those hankies on stand-by. You may need them.

No Offence (C4, 9pm)

THE race to nail the Attah gang sows seeds of mistrust and secrecy between officers Deering, Dinah and Joy, and later, controversy surrounds Deering when she recklessly forces mouthy Donna Calvert to infiltrate the Attah gang. Elsewhere, Dinah has to investigate when a seemingly peaceful staff protest at an abortion clinic takes an unexpected turn for the worse, and quickly starts to spiral out of control. Starring Joanna Scanlan, Elaine Cassidy, Alexandra Roach and Claudia Adshead.

Revenge (NOW TV/Sky On Demand)

GRITTY, realistic TV dramas are all very well, but sometimes we just want to watch rich, pretty people scheming against each other - and this delightfully soapy series definitely fits the bill. Emily VanCamp stars as Emily Thorne, a glamorous young woman who rents a beach house in the exclusive Hamptons resort, next door to the wealthy Grayson family's mansion. But what her new neighbours don't know is that Emily is really Amanda Clarke, whose father died in prison after being framed by the Graysons – and she's here to take her revenge on the clan's matriarch Victoria (Madeleine Stowe). If you find yourself hooked on the Dynasty-style goings on, the good news is that all four seasons are available to binge watch.

Viv Hardwick