Stepping out of the Tube train onto the platform of my usual station, I was surprised to see a clear plastic garbage bag taped to the wall. It was filled with free newspapers, the most common detritus of the Underground. I saw another taped bag ten metres along the corridor.

One of the quirks of the Underground is that there are no bins — not a single one. I found this out early on in my Tube career when, suffering severe sniffles, I couldn’t find a bin to dispose my mass of used tissues.

It’s because of terrorism. Even before 9/11 and 7/7, since the 1970s the Underground has been under attack from groups like the IRA. Bins are potentially handy places to hide bombs, I guess.

Even without bins, you’d be surprised at how clean Underground stations are. I don’t remember any litter in stations, except for occasional newspapers. Each station is patrolled by an army of cleaning staff, picking up papers and bottles, mopping up pavement pizza…

As I climbed up the escalators, an announcement on the PA system explained the taped up rubbish bags.

‘Attention! There are no cleaning staff at the station today. Please take all your litter with you, including free newspapers.’

I expect that by the end of the day, the station looked like a landfill.