It was on the Circle Line – in the days when it was a ‘circle’, before they mutated it into that saucepan shape, with its Hammersmith extension - between St James Park and Westminster. He was sitting there, staring across the carriage, his expression blank, his eyes revealing no connection between himself and the almost empty carriage.

There were just four of us – me, him and his two kids.

Whilst he was silent, his children were manic, screaming and shouting, running up and down the carriage, jumping onto seats, at one point trying to remove one of the advertisements from its frame above the window.

They repeatedly raised and lowered the sliding window on the connecting door and howled with laughter as hot, stale air rushed through the carriage.

And all this time, he just sat, oblivious to the chaos his young charges were creating.

When they started to use balled up pages of newspaper in a mock snowball fight I lost it.

‘For fuck’s sake,’ I screamed at them. ‘Just sit down.’

It didn’t help; in fact it made matters worse. They turned their attention on me and began pelting me with Metro snowballs. And when I stood up the smaller child laughed at me and said, ‘Prat,’ – which I thought almost eloquent for a seven-year-old – before lobbing another crumpled sheet of newsprint at me.

I took the single pace to their father. ‘Can’t you do something with these two?’

He had no idea what I was talking about. ‘Sorry?’ he said.

‘Your kids, can’t you shut them up?’

‘Yes, I‘m sorry.’ As he looked at me, his eyes were brimming with tears. And when he spoke again his voice had dropped to a whisper. ‘It’s their mother,’ he said. ‘She’s just died… and I don’t know how to tell them.’

I got out at Westminster: I really wanted Liverpool Street.