When I lived in London it seemed entirely normal that different Underground trains, like overground ones, left from the same platform. I could never understand why this baffled visitors; you checked the board, simple as that. Then last time I was in London after nothing more than a glass of water over lunch (I was driving the pushchair) I boarded a Tube, sat down to read my newspaper (the pushchair occupant was asleep) and failed to notice I was on the wrong line heading in the wrong direction until I looked up and found I was in the middle of nowhere. This does not happen in Paris. Only one line arrives - from the left - and departs - to the right - from any given platform. If you have identified the right line, you cannot catch the wrong train, you can only go in the wrong direction. I blamed the London incident on having been out of the country too long.
Then there was the 'TGV incident', which I promised not to mention again.
Now I have notched up a hattrick. I had to take La Fille to her optician to get the lenses changed in her glasses. I have been to the same shop at Place de la Nation more than a dozen times, by metro, by bus and even on foot when I am feeling especially energetic; it is a three mile hike. For some reason, however, I took a metro to Place d'Italie in an entirely different part of Paris and some way across the other side of the River Seine? I don't know why, any more than I can explain London or the TGV incident. I am not normally so dozy. It gets worse; I didn't notice my mistake this time until I left the Metro at Place d'Italie where there just happened to be a mass demonstration and march. The station and surrounding streets were packed with students protesting against education reforms and making a lot of noise about "social solidarity".
Was there a single show of solidarity as I struggled up the station steps La Fille in one hand, pushchair in the other as they jostled and shoved past me? Was there hell.