Psychoville

BBC Two, 10pm

Of all the episodes in this strange series, this is the strangest and most fascinating to date. It is a homage to Alfred Hitchock’s 1948 film Rope with James Stewart, which told the story of two young men who murdered a classmate, put his body in a wooden chest and invited the victim’s friends and family round to dinner. It was a daring and experimental film, shot as though it were taking place in real time using long, unbroken takes. The same technique is used here, with a single location and only three characters — the comic killers (Reece Shearsmith and Steve Pemberton) and their unfortunate victim (Mark Gatiss) — shot in two long takes. The effect is theatrical, claustrophobic and totally mesmerising. One of the greatest pleasures of watching television is coming across a complete surprise; in the fast-forward world of snappy editing, tonight’s episode has a shocking originality.

How the Celts Saved Britain

BBC Two, 7pm

The British, according to the historian Dan Snow, have traditionally regarded Ireland as a wild, unruly and uncivilised place badly in need of modernisation and pacification. This, he argues, is totally wrong-headed. Some 1,500 years ago, while England was being torn apart by illiterate pagan warrior tribes during the Dark Ages, Ireland had been converted to Christianity by St Patrick. Crucially, with Christianity came literacy and education, and the monasteries of Ireland became centres of learning and culture. This two-part series, which continues tomorrow night, has been made on a tight budget but Snow is a model of clarity and restraint.

Celebrity MasterChef

BBC One, 8pm

It’s still wide-open in the finals as the three contestants are flown to Morocco and have to master traditional cooking techniques as well as exquisite fine dining. The standard of cooking is so high that it’s off the scale. Jayne Middlemiss continues to be a woman on the edge of a nervous breakdown and Wendi Peters has started talking to herself, but they still end up producing the goods. But the dark horse of the night is Iwan Thomas, who serves up a stunning chicken, lemon and olive tagine cooked on an open fire in Morocco, and then trumps his triumph back in London by producing an immaculate Italian fish stew in front of five Michelin-starred chefs. “The dish,” says Michel Roux Sr, “is really what you wish you could cook in your own restaurant.”

Gerry’s Big Decision

Channel, 9pm

Tonight, Gerry Robinson decides whether to use his own money to salvage two more loss-making companies. One is a furniture manufacturer in Lancashire with an 80-strong workforce which, if forced to close, would mean the collapse of an entire village community. The other is a manufacturer of pies in Devon. Apparently they are among the most delicious pies that you can buy anywhere in the country, but the company has never made a profit and it has no underlying assets. It takes Robinson roughly 45 seconds to figure out what is going wrong with both companies. But whether or not these problems can be sorted out with a simple of injection of cash is a different matter.And beware of Robinson’s twinkly charm and air of pained concern. He ain’t no charity.

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