The precocious boy is talking loudly (and precociously) to his father (?) in the seat behind me. I manage to zone most of it out and concentrate on my book, but am distracted when I hear him suggesting to his father that they "do some French". This should be interesting. Having two seats to myself, I shuffle forwards so that my ear is conveniently located between the two seats, maximising my eavesdropping opportunity.

Most of the French exercises they do are correct to my trained ear (bar a few dodgy pronunciations), but I notice the father fluffing the position of the negative when constructing a sentence with a reflexive verb in the perfect tense.

Later, as we approach Clapham Junction, I move towards the front of the train. Time is tight - there is a slim hope that I will make my connection at King's Cross, but only if I minimise the amount of platform I have to walk along once I get to Waterloo.

I choose my exit point, and am joined in the "vestibule" by a woman. She presses the "open" button on the toilet beside us, and the door glides across to reveal a man having a wee. We both avert our eyes and stifle a snigger. The man, now re-buttoned, emerges and checks the door. Somewhat bewildered, he directs his explanation to us: "It just came open...". My conspirator and I shrug innocently, and he makes his exit.

I smile. "He must have forgotten to press the "Lock" button," I suggest, to salve her conscience. We share our opinions of new-fangled toilet door devices, agreeing that a mechanical lock is infinitely preferable to the possibility of a door sliding open whilst one is "otherwise engaged".

I ask her if she knows what's happening with the tube at Waterloo. I had a feeling there was some restriction about which exits were usable, but couldn't remember the details. She looks at me blankly. "I haven't been up here for years, I've no idea!". I ask her which way she's going. "St Pancras. I'm visiting my grandmother in Bedfordshire. I've no idea how to get there, though..." Since I'm going to King's Cross and know exactly which way to go, I tell her to follow me.

I guide her down the escalators through the throng of the Friday evening rush hour (she stands on the left - I hastily usher her over to the right) . "Head for the Bakerloo line - it's an easy change at Oxford Circus...". Old habits die hard.

We make our way onto the platform, and I stomp purposefully to the opposite end, away from the entrance, where there are fewer people. Old habits die hard.

The Bakerloo line is fairly empty, but we're in for a treat on the Victoria line at Oxford Circus. I've barely time to go all nostalgic at the destination of our train ("Walthamstow, my Walthamstow!") before we are crammed together into an altogether less airy vestibule than that offered by South West Trains. I have just enough space to peer down at my watch, concerned.

"Do you think you'll make the train?" she asks, knowing how little time I have. "Nah..." She, on the other hand, will arrive with time to spare.

As we leave the tube and head for the mainline, it's 17:43. My train leaves King's Cross at 17:45. Once we've negotiated the barriers and gone our separate ways, I emerge onto the concourse, looking hopefully at the departure board. First train on the board: 17:50 to Peterborough.

My train has departed... but, as I discover when checking my phone and finding several missed calls from when I was deep underground, the friend I'm meeting there has not. We get some supplies from M&S Simply Food and pile onto the 18:15 instead. Our weekend has begun.