Sir John was the first to posit the existence of metamaterials - materials with a negative refractive index which can have a spatial resolution below that of the wavelength permitting the possibility of invisibility.
The idea of metamaterials came to him while working on radar for Marconi. "I think it illustrates yet again the unpredictability of research," says Sir John, “when you have an original idea, if it's a really good one, you don't know where it's going, because it's bigger than you are. I had no idea when I started with a few simple notions that it would actually go so far."
In 2006, he published an idea for an invisibility cloak.
IoP President Professor John Knight says Sir John’s work is “the most exciting that I've seen in optics in a generation."