SOME things are just not meant to be. Take smell-o-vision. A duff idea in cinemas, it didn’t work on TV either. You will never be more glad of that failure than when watching The Secret Science of Sewage (BBC2, Thursday, 9pm).

Presented by Dr George McGavin, Glasgow-born, Edinburgh-educated entomologist and author, and Dr Zoe Laughlin, there is no hiding what the subject is, much as we would want to. As McGavin says, sewage is something humans are hard-wired to avoid. Little wonder when you consider some of the nasty stuff lurking within, and that is before we get to the dreaded wet wipes (responsible for 75% of all blockages, since you ask.

The good doctors have been given “exclusive access” to Minworth Sewage Treatment Works in Sutton Coldfield, though I cannot imagine there was a lot of competition. Their task: to discover whether there is more to the brown stuff than we might think. Could one person’s sewage eventually be another’s energy source? Might sewage hold the key to tackling the next superbug? Could it even save the planet’s food supply?

Obviously there are answers to be had here, otherwise our intrepid two have had a wasted trip.

The sewage is followed from its arrival, through the filtration and cleansing process, and out the other side. Human waste amounts to less than 2% of raw sewage so there is not a lot disgusting to see, but there is enough to avoid having your tea while watching.

This is particularly the case when the inspection hatch at the filtration stage is opened to reveal some of the stuff that is screened out early on.

Dr Laughlin’s guide at this point is Andy the technician. Laughlin expects he must be used to it by now. Not quite. “When you open it up and see a dead rat hanging by the tail it’s still a bit of a shocker,” says Andy.

With the aid of animated guides and interviews with scientists in the field, the doctors discover all the wonders to potentially be had. They make a watchable presenting duo, each as enthusiastic for discovery as the other.

Oddly, it is some way into the programme before anyone mentions the smell, which is at its most pungent during the settlement process, as Dr McGavin discovers when handed a container full of sewage. You really don’t need smell-o-vision to do the scene justice. The look on his face is proof enough.

It takes a while to tune in to The Flight Attendant (Sky1, Friday, 9pm, full series on Now TV). Not because this thriller with comic undertones is hard to follow. Far from it. But it is set in this weird world where people get on and off planes as if they were buses, go to clubs, restaurants, meet others, have fun, nobody wears a mask. Vaguely rings a bell, doesn’t it?

Cassie (Kaley Cuoco from The Big Bang Theory) is the eponymous high flyer with a tendency to get so drunk it is not uncommon for her to wake up with a stranger. On a flight from New York to Bangkok, she and a first class passenger click over a love of Russian literature, and a few other things besides.

Later, there’s a date, dinner, bed, and she wakes the next day into a nightmare. There’s a guy in her sheets again, but this one won't be explained away easily.

An actor since childhood, Cuoco is successfully channeling her experience into programme making. She was executive producer on the TV series Harley Quinn, and takes the same role here. Joining her in the predominantly female cast is Rosie Perez, playing Cassie’s best friend and fellow flight attendant.

There’s a touch of Hitchcock about The Flight Attendant, from the graphics in its opening titles to the “anything can happen” air. But the fast paced editing, the frequent breaking of the fourth wall, and the poptastic soundtrack, place the show firmly in the feminist 2020s.

Cuoco is terrific in the lead as the woman who, when not drinking herself into oblivion, insists she is living a “super fun life”. Flashbacks to the past suggest the reality is far more complicated than she can handle. Who is she really and what did happen that night in Bangkok? You’ll be intrigued enough to make this your new must-see.

A little bit of Hollywood by way of Scotland arrives on The Great Celebrity Bake Off for Stand Up to Cancer (Channel 4, Tuesday, 8pm), and we don’t mean Paul Hollywood, the judge. James McAvoy (X-Men, Atonement, Split) is the name and donning a pinny to raise money for charity is his game.

In this, week two, he is joined in the tent by comedian David Baddiel, the singer Anne-Marie, and Olympic gold-medalist Dame Kelly Holmes. Hitherto not known for his baking skills, McAvoy could be a revelation, or a collapsed sponge with a soggy bottom. On Bake Off it can go either way.