My recording was interrupted by some kind of communal activity: the guardians and children gathered together for approximately twenty seconds and then moved to the other end of the playground, where my view of them was obscured by a central island of foliage. I followed and sat where I could observe them again, but they did not resume their play. I decided to wait and used the time to change the video resolution on my phone in case there was an opportunity to film a longer segment. Due to my focus on the camera-operating task, I did not notice the approach of two uniformed male police officers.

In retrospect, I may not have handled the situation well, but it was an unfamiliar social protocol in unexpected circumstances driven by rules which I did not know. I was also struggling with the video application which I had downloaded because of its superior compression algorithm, without due attention to its user-friendliness.

‘What do you think you’re doing?’ This was the (marginally) older policeman. I guessed they were both in their thirties, and in good physical shape—BMIs approximately twenty-three.

‘I think I’m configuring the resolution, but it’s possible I’m doing something different. It’s unlikely you will be able to assist unless you’re familiar with the application.’

‘Well, I guess we should get out of your way and leave you with the kids.’

‘Excellent. Good luck fighting crime.’

‘Get up.’ This was an unexpected change of attitude on the part of the younger colleague. Perhaps I was seeing a demonstration of the ‘good cop, bad cop’ protocol. I looked to Good Cop to see if I would receive contrary instructions.

‘Do you also require me to stand up?’

Good Cop assisted me to stand. Forcefully. My dislike of being touched is visceral, and my response was similarly automatic. I did not pin or throw my assailant, but I did use a simple aikido move to disengage and distance him from me. He staggered back and Bad Cop pulled his gun. Good Cop produced handcuffs.

At the police station, the officers sought a statement in which I conceded that I had been in the park observing children and that I had resisted arrest. I was finally given an answer to the obvious question: what had I done wrong? It is illegal in New York to enter a designated children’s playground without the company of a child under the age of twelve. Apparently there was a sign posted on the fence to that effect.

Incredible. If I had actually been, as presumably suspected by the police and anticipated by the lawmakers, someone who gained sexual satisfaction from observing children, I would have had to kidnap a child in order to gain entry to the playground. Good Cop and Bad Cop were not interested in this argument, and I eventually provided an account of events that seemed to satisfy them.

I was then left alone in a small room for fifty-four minutes. My phone had been confiscated.

At that point an older man, also in uniform, joined me, carrying what I guessed was the printed version of my statement.

‘Professor Tillman?’

‘Greetings. I need to call a lawyer.’ The time spent alone had been useful in allowing me to collect my thoughts. I remembered a 1-800 phone number for criminal lawyers from a subway advertisement.

‘You don’t want to call your wife first?’

‘My priority is professional advice.’ I was also conscious that news of my arrest would cause Rosie stress, particularly as the problem was still unresolved and she could do little to help.

‘You can call a lawyer if you want. Maybe you won’t need one. You want something to drink?’

My answer was automatic. ‘Yes, please. Tequila—straight up.’ My interrogator looked at me for approximately five seconds. He made no signs of getting the drink.

‘Sure you wouldn’t like a margarita? Maybe a strawberry daiquiri?’

‘No, a cocktail is complex to prepare. A tequila is fine.’ I suspected that they would not have fresh juice available. Better a neat tequila than a margarita made with lemon syrup or sweet-and-sour mix.

‘You’re from Melbourne, Australia, right?’

‘Correct.’

‘And now you’re a professor at Columbia?’

‘An associate professor.’

‘You got someone we can call to verify that?’

‘Of course. You can contact the Dean of Medicine.’

‘So you’re a pretty smart guy, right?’ It was an awkward question to answer without appearing arrogant. I just nodded.

‘Okay, Professor, answer me this. With all your intelligence, when I offered you a margarita, did you really think I was going to go to the tearoom and squeeze a few limes?’

‘Lemons are fine. But I only asked for a tequila. Squeezing citrus fruit for cocktails seems an inappropriate use of time for a law-enforcement professional.’

He leaned back. ‘You’re not kidding, are you?’

I was under extreme pressure, but conscious that I must have made an error. I did my best to clarify.

‘I’ve been arrested and am at risk of incarceration. I was unaware of the law. I am not intentionally making a joke.’ I thought for a moment, then added, only because it might reduce the chances of jail and consequent low-quality food, dull conversation and unwanted sexual advances, ‘I’m somewhat socially incompetent.’

‘I sorta figured that out. Did you really say “Good luck fighting crime” to Officer Cooke?’

I nodded.

He laughed. ‘I’ve got a nephew a lot like you.’