“By the way, your house is slowly filling with particles as we speak.” It isn’t exactly what you want to hear sitting in your kitchen on a dank wintry afternoon. I am discussing the toxicity of the atmosphere in my south London flat with air pollution scientist Dr Gary Fuller over lemon drizzle cake.

Because when you learn you have knocked nearly two years your life simply by virtue of growing up in smog-filled London, the only thing for it is cake. Between us on the table is a little white plastic implement which is apparently gauging the number of harmful particles in the air.

As we talk the corresponding live graph on an app on Dr Fuller’s phone slowly rises. “Your flat appears to be about as polluted as most of my journey here,” says Dr Fuller, calmly, as if he hasn’t just essentially told me that I my home isn’t any safer than if I had pitched a tent at the side of Oxford Street.

“In fact, there were areas when I was on the bus around Oval on my way here when I was in the green. Now I’m in the orange. So it was less polluted there than it is here.” He concedes after some nervous questioning on my part that this may be down to the fact that speeding through London on the no. 59, he was never in one place long enough for the sensor to pick anything up.