9pm, Sky Atlantic
A third series for Jez Butterworth’s daft but engaging semi-historical drama. Three years have passed since the Roman invasion and things seem to be settling down. David Morrissey’s Aulus is certain he has Druid head honcho Veran (Mackenzie Crook) over a barrel – and he’s letting him know, in a manner that may come back to haunt him. Meanwhile, Cait is considering her next move. As ever, Britannia’s tone is uneven, but it retains a profane, unpredictable and manic edge that is very much its saving grace. Phil Harrison
Paralympics: Opening Ceremony Live
11.30am, Channel 4
The Tokyo Olympics opening ceremony was a sombre affair, reflecting the unusual circumstances surrounding this year’s games. It will be interesting to see if the Paralympic equivalent adopts a similar tone. Ade Adepitan presents live coverage alongside Baroness Tanni Grey-Thompson. PH
Secrets of the Museum
9pm, BBC Two
The final episode of this behind-the-scenes series at London’s Victoria and Albert Museum follows curators as they try to discover the provenance of a painting of Buddha, newly acquired for their permanent collection. Digital archivists also set about 3D-scanning a Wedgwood Portland Vase, to be displayed online. Ammar Kalia
Love Your Cottage Garden Special
More horticultural hints from Alan Titchmarsh and the gang. Tonight, he’s showing off his mixed border and explaining how anyone can assemble something similar. To demonstrate, Titchmarsh’s team are tackling the messy cottage plots of a pair of nurses. PH
Unbelievable Moments Caught on Camera
A new series transforming an aimless YouTube browse into an hour of light entertainment as the ever-urbane Alexander Armstrong marvels at odd, scary, dramatic video clips from around the world. Tonight, a skydiver has a mid-air collision and a woman is rescued from a burning car. PH
24 Hours in A&E
9pm, Channel 4
Derren, who broke his ankle while trampolining with his daughter, and former lollipop lady Angela (attacked by one of her cats while shouting at a fox), are just two of the cases featured in this compilation show, looking back at patients and staff from south London’s King’s College Hospital and St George’s. Ali Catterall
Hallam Foe (David Mackenzie, 2007), 1.15am, Film4
Who’s that kid on the roof? It’s Jamie Bell’s teenager Hallam, grief-stricken at the apparent suicide of his mother. Taking a job at an Edinburgh hotel, he starts spying from the gables on personnel manager Sophia Myles, the spitting image of his mum … A beguiling blend of disturbed coming-of-age drama and romance. Paul Howlett
Cycling: Vuelta a España 1.35pm, Eurosport 1. From Roquetas de Mar to Rincón de la Victoria.
T20 Blast Cricket: Yorkshire Vikings v Sussex Sharks 6pm, Sky Sports Cricket. The first quarter-final from Chester-le-Street.
Champions League football 7.45pm, BT Sport 2. A qualifying play-off between two teams to be announced.