Apps that block online adverts have never been so popular - they are the most-downloaded on Apple’s new operating system, iOS 9, which launched last week. But if you already find big banners and self-starting videos annoying, what’s coming next is truly terrifying.

Advertisers are developing ways of tracking our eye movements through the forward-facing camera on our phones. When that happens, there will be nowhere to hide: what you look at gives away what you’re really interested in. It’s even possible to predict the spot the eyes are heading to and plant a nice juicy advert there for when they arrive. This could make for a very uncomfortable browsing environment.

We’re good at reading eye movements in other people – if someone glances at a packet of biscuits, we’ll offer them one – but you can’t always control where your own eyes go. For example, when you meet someone of any gender, you first look at their eyes, then glance at their genitals, then return to their eyes. You might claim you don’t, but everyone does. Let’s just hope this won’t give the advertising companies any more ideas.

Dr Daniel Glaser is director of Science Gallery at King’s College London