There really was a mighty robot called Eric, and he really was built by Captain W Richards and his friend Alan H Reffell. Eric made his first public appearance at an exhibition in London in 1928. Originally the Duke of York was due to open the exhibition, but when he couldn’t make it Richards and Reffell decided to build a robot to take his place.

Eric’s nervous system was four kilometres of wire. His skin was aluminium. His bloodstream was 35,000 volts of electricity, which made his teeth shoot sparks. He could stand, sit and answer fifty questions. He couldn’t walk, though. Captain Richards liked to say this was because Eric was only six months old and hadn’t learned to walk yet.

Mr Reffell imagined that Eric would be able to get a job – maybe answering the phone in an office, or giving out information in a railway station. But from his first appearance he was a sensation.

‘Aluminium Man Startles London’ ran one headline.

An American paper published a full-length interview with him, in which Eric revealed that he didn’t drink, or smoke, or run around nightclubs at night.

‘Girls!’ declared the interviewer. ‘Eric is the perfect man.’ And he compared him to a chivalric knight.

Then, during the war, Eric disappeared. Maybe someone – worried he might be damaged during the bombing – hid him in a cellar for safekeeping. Eric was almost forgotten. Until, in 2017, the London Science Museum had an exhibition of all the greatest robots from history. The curator – Ben Russell – found some of the plans for Eric and asked the robot maker Giles Walker to rebuild him. He even let me come and see Eric while he was being rebuilt. It was an amazing experience. Thank you very much, Ben. And thanks to my son, Xavier, who came with me and asked much more interesting questions.

When Eric was first created, he looked like the future. By the time Ben and Giles rebuilt him, he was history. He was a mechanical Rip van Winkle. He fell asleep in a world where hardly anyone had seen a robot. When he woke up, the world was full of robots. But none of those robots looked anything like him.

As I type this, I can see a robot lawnmower wandering around next door’s back garden nibbling the grass like a big plastic hedgehog. Modern robots come in all shapes and sizes – from next door’s hedgehog to Oppy, the robot that roamed the surface of Mars taking photographs and rock samples for fourteen years. It only stopped when it was swamped in a Martian dust storm. Oppy’s last message was, ‘My battery is low, and it’s getting dark.’

We have robot checkouts in supermarkets, and robot cameras quietly watching our streets. The internet is run by a vast army of invisible ‘soft’ robots, who monitor our spending, translate languages, recommend books and holidays. More importantly, some of the things we have learned in making machines that act ever more like humans have in turn inspired us to make better and better artificial parts for our own bodies.

Prosthetic legs now often have Bluetooth to help regulate the speed and the length of your stride when you walk on them. They’re also often made of carbon fibre, which feels warmer and more ‘human’ than wood or metal. Myoelectric and biometric technology uses signals from our own muscles to operate new hands and arms. Alfie’s story was inspired by the true story of Daniel Melville’s ‘hero arm’, which was built for him by Joel Gibbard and Samantha Payne’s company Open Bionics, whose motto is ‘welcome to the future, where disabilities are superpowers’. Daniel’s amazing arm was based on the arm of his favourite hero: Adam Jensen, from the video game Deus Ex, and he was kind enough to talk to me about how it feels and what it takes to be part-bionic. Massive thanks to Daniel.

As well as speaking to a really bionic person, I also got help from a real robot-maker. His name is Professor Andrew Vardy and he teaches at Memorial University in Canada. His robots are the exact opposite of Eric – they’re tiny, tame and very helpful to humans.

It’s a pity, of course, that one reason we need to learn to replace human hands and legs is that humans spend a lot of time, money and technology injuring other humans. Shatila – like thousands of other children – lost her foot to an unexploded landmine. Landmines are planted during wartime, but they don’t vanish or stop working when the war is over. They are a kind of terrible legacy – staying in the ground, hurting innocent people for many years afterwards. Shatila is from Bosnia – a place I visited shortly after the war there had finished in 1995. People were already trying to clear the landmines then. More than twenty years later that work is still not finished. There are landmines like this in countries as far apart as Cambodia and Somalia. Some of the landmines that are still dangerous in Egypt date back to the 1950s. They’re still killing people today.

Of course, one of the good things that modern robots can do is help us get rid of landmines.

Eric wasn’t really a robot. He was what we call an automaton. He couldn’t go off on his own like Oppy. He couldn’t make decisions like next door’s lawn mower. But, by building him, Reffell and Richards made us think what a real robot might be like. This is always happening in science. Someone has to imagine what it would be like to fly to the moon before anyone starts building a rocket. Dreaming is every bit as important as building.

Modern robots do lots of good, important work. But they wouldn’t exist if people like Richards and Reffell hadn’t had fun playing about with ideas in an old garage in Surrey.

I knew nothing about Eric until my friend and editor Sarah Dudman showed me some clips of him speaking – you can still find them on YouTube. Normally Sarah reads my books when they’re almost finished and shows me how to make them better. But this time she was there at the beginning as well as the end. When the idea got lost and started to rust – like Eric – she dug it out of its hiding place and sprayed it with WD-40, and got it going again. Thank you, Sarah – like never before.

Thank you too to the wise and patient Venetia Gosling, who let me keep going at this book until the story was right.

And of course to the mighty Steven Lenton, who brings all my imaginings to life.