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Boffin who says Harry Potter's magic cloak owes more to Peter Pan than Hogwarts

Following the stage debut of Harry Potter and the Cursed Child, Racheal Sigee reports on how Sir John Pendry's radical invention isn't for sneaking about in Hogwarts Library’s restricted section... it showcases some very serious research.

Audiences at the Palace Theatre in London were wowed last night by the spectacle of Harry Potter and the Cursed Child. With reports of stunning special effects and "How did they do that?" moments it seems the excited fans were as happy at the visual brilliance of the theatre production as the return to Hogwarts.

Surprisingly though, the man who has come closest to creating a real-deal version of Harry's famous invisibility cloak says his literary icon is Peter Pan, not The Boy Who Lived.

Imperial College London's Professor Sir John Pendry was the star of the scientific show in 2006 when he published research which showed for the first time how a cloaking device could be used to conceal an object, although we won't be donning our own cloaks any time soon: Pendry's work was strictly theoretical.

The 73-year-old theoretical physicist isn't too annoyed by the Potter association unless people "get a little bit silly about it", especially as he has never read the books and was filled in by his wife of the connection.

"I'm regarded as a rather serious person, often quite po-faced, but sometimes I have a bit of fun with cloaks," he explains. "I try to be careful to explain that it's there to showcase some very serious science but it's done the job of bringing people who wouldn't normally be interested to science."

Pendry won the Institute of Physics' Isaac Newton Medal in 2013 and his work on cloaking involved creating "a new class of materials" called "metamaterials". It was inspired by his realisation that you could alter a material's properties by changing its structure rather than its chemistry. For example, silver can be polished to be reflective but when ground into nano-particles it appears black.

This invention "set the electromagnetic world on fire" - even a decade on he is speaking to me from a conference in Spain about metamaterials, with more than 1,000 attendees. Pendry assures me, though, that the concept of his invisibility cloak is really very simple.

"If you think of a stone in a stream, the water naturally flows around the stone, and the flow of the water nicely closes up behind. Anyone a way down the stream has no idea the stone is in the water. That's what we want to do with light. But light doesn't flow around objects, it naturally bounces off the object and refracts. The trick is to make light flow like water."

Pendry says of his work: "Our icon is not Harry Potter, it's Peter Pan, as one way of explaining it is to say you're not just making something black; the real trick is taking the shadow away."

Although, as he puts it, "a few of my colleagues get overexcited", the cloak idea was used to display the technology he and his team had developed rather than give us all superpowers. "No doubt you're hoping I'll say the kids will be running around in cloaks? I'm afraid not."

Practical uses of elements of the technology involved include satellite communications - a company called Kymeta has had funding from Bill Gates for a project which uses metamaterials in this context - and MRI scanning.

But in terms of the actual cloaks, Pendry is keen to point out that he's the ideas man. "I'm a theorist so I have all the fancy ideas but to actually turn it into reality, I have a fantastic collaboration with a team based at Duke University in North Carolina."

If they were to bring his research to life the most obvious use would be in the military, but Pendry says "people have run off in all directions" with his research.

"As far as I'm concerned, the theory behind cloaking is done. The formula is out there - people have applied it to sound, to light, to water waves. One of my former post-docs has proposed a cloak for earthquakes - he's actually persuaded an oil exploration company to drill some holes and do an experiment."

Indeed now, Pendry is working on what he calls "anti-cloaking" on the premise that if you can guide light away from an object, what if you want to attract light? It's no Marauder's Map - but it might just prove more useful.


Following the stage debut of Harry Potter and the Cursed Child, Racheal Sigee reports on how Sir John Pendry's radical invention isn't for sneaking about in Hogwarts Library's restricted section . . . it showcases some very serious research

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