What to watch tonight: TV choices - 30 October

Ambassadors, Poirot and Gregg Wallace's Supermarket Secrets

David Mitchell stars in Ambassadors, which continues on BBC2 (BBC/Big Talk)

Ambassadors

9pm, BBC2

Tom Hollander guests in the Rev writer James Wood's diplomatic comedy. Hollander plays a minor royal invited to Tazbekistan in order to help secure an oil drilling contract. David Mitchell and Robert Webb star.

Autumn's Supermarket Secrets

9pm, BBC1

Gregg Wallace returns with his occasional series about the workings of our supermarkets, visiting a pumpkin patch (okay, a vast prairie) in Cambridge producing many of the millions of the orange squash that need to be shop-ready for Halloween. Plus, why the fruit and veg are always found at the supermarket entrance.

Agatha Christie's Poirot

8pm, ITV

"Dead Man's Folly" continues the concluding quarter of episodes of the crime drama that makes Midsomer Murders seem like The Wire.

The Dark Matter Of Love

10pm, BBC4

Claudio and Cheryl Diaz from Wisconsin decided to adopt three Russian children who had grown up in institutions. Sarah McCarthy's film tells of how the children were unable to bond with their new family and how the Diazes turned to developmental psychologist Dr Robert Marvin to find a scientific way to teach the youngsters how to love for the first time.

The Culture Show: Samuel Johnson Prize 2013

10pm, BBC2

Biographies of Margaret Thatcher, Italian poet Gabriele d'Annunzio and Fabian Ware, who founded the Imperial War Graves Commission, are among the shortlisted non-fiction.