The Great Wall of China: The Hidden Story – Secret History; Homeland; Remember Me – review

Some big revelations in The Great Wall of China: The Hidden Story – Secret History (Channel 4, Sunday). First, there’s not just one wall, but many. The Great Walls of China, at least 16 of them, built over 2,400 years by successive emperors and dynasties. Total length: 21,000km, three times longer than previously thought, longer than the distance between the poles. Eat your heart out Hadrian, Pink Floyd etc.

The idea was the same as Hadrian’s, though: to keep out uncouth marauding neighbours from the north: Scots, Mongols, they’re much of a muchness. Here are some, reconstructed Mongols, galloping thunderingly on horseback and firing their bows. Ooch aye the noo, Genghis, good arrers.

So how did they come up with the new figures? Technology, that’s how: aerial mapping, satellite images, 3D models, GPS, laser scanning. And drones. The helicopter drone has become an essential piece of kit in the making of television documentaries like this; they breathe new life into the very ancient, using the very modern. These drones are good. They’re got five cameras and loads of mapping stuff – you can just fly them along the wall and they come back with everything you need to know about it.

Also required is a lot of martial music and a script full of drama and superlatives. It is “THE MOST EXTRAORDINARY feat of engineering in history”; “one of the MOST ICONIC man-made structures on the planet”; they’re using “GROUNDBREAKING science” and “CUTTING EDGE chemistry” to uncover the enigma at the heart of the WORLD’S GREATEST MEGASTRUCTURE”.

Always good to get a megastructure, a mega-something, anyway, in there. Basically it’s awesome. If the Great Wall(s) of China was a creature that swam in the sea in would be a great white shark, an APEX PREDATOR.

I could do with less hyperbole. It doesn’t need it; it’s interesting enough in its own right. What else have they discovered, then, using all their groundbreaking science, technology and code-breaking? That they had a complex signalling system, early Chinese semaphore, to warn of attack. A red flag up the pole meant 50 Xiongnu coming. Three red flags? 200 Xiongnu coming. Big bonfire? 1,000 Xiongnu coming, etc. Xiongnu were terrifying early raiders – early Scots, basically. Big bonfire, squeaky bum time, in other words.

My favourite thing about the wall, and about the programme, comes from the CUTTING EDGE science. Top chemistry professor and expert in ancient building materials Dr Xiang has taken samples from the Ming dynasty wall, which was built after the Mongols – who had occupied China for over a century – were finally sent packing. He has found that the secret of the Ming wall’s strength and longevity lies not in the bricks but in the mortar. The whitish colour of the mortar was said, in legend, to be because it was made from ground-up human bones. Not so, says Xiang. The secret ingredient that went into the mortar, kept the WORLD’S GREATEST MEGASTRUCTURE standing for hundreds of years? Sticky rice. Isn’t that great? Take note, modern brickies: a sprinkle of rice in the mortar and it’ll last for ever; Ben’s your uncle.

Just the one disappointment: you can’t see the wall, or walls, any of them, from space. That’s a lie.

Thank God that in Homeland (Channel 4, Sunday) Carrie has figured out her meds were being messed with. Because I’m not sure I could have taken more than one episode of Claire Danes ACTING MAD. Eyes popping out of her head, all that darting around, it’s too much. I’m also glad Brody turned out to be a hallucination, not the actual Brody. Because not only am I not missing him, I think it’s actually better without him. Certainly the whole thing has found new momentum and direction since he was (sadly) hanged*. This series has been brilliant. Like when someone you think is indispensable leaves the place you work at, and it’s actually better without them.

Anyway, this is not about Brody – this episode belongs to Saul, showing a previously unseen steely badassness. So hard! With that nail, and the guard? Go Saul! Oh … until he’s recaptured, by a bunch of red triangles. It’s all just a big video game isn’t it, modern warfare?

Remember Me (BBC1, Sunday)? Drip drip drip, ominous black clouds, drip drip drip, even more ominous, blacker clouds. Plus a hint of the mysterious orient. Are you going to Scarborough Fair? Parsley, sage, rosemary and thyme ... not the Simon and Garfunkel one, but another version, lots of other versions. Older, spookier versions.

Where’s Michael Palin gone, though? Boo! There he is. Woooooooooo. Scary.