A firm hand on my shoulder caused me to stop firing questions at young men being frog-marched into a police truck by OMON riot police near Pushkin Square.

I turned around and saw it was a policeman. Assuming he just wanted me out of the way, I backed off. But his grip tightened and he spun me around and pushed me toward the truck.

"What the hell have I done?" I shouted. I wasn't looking for a response. I just wanted to register with the police and hundreds of onlookers that I had done nothing wrong.

A police officer manning the door asked me my name, which I gave, and without waiting to be shoved into the back of truck, I clambered inside.

Somehow police managed to cram 12 of us into the tiny, stifling gray cell, which was lined with two benches. Two weak bulbs in the ceiling provided little more than candlelight.

The atmosphere in the truck was strangely jovial. It was as if everyone accepted that this was the inevitable outcome of the Dissenters' March from Pushkin Square on Saturday. Everyone knew they would be released in a matter of hours. I tried in vain to strike up a conversation with the others, none of whom looked older than 25.

We sat there for about 30 minutes before being driven off to the Zamoskvorechye police station. During the ride, a young man opposite me made a call from his cell phone, apparently to his girlfriend.

"God knows, must have been some kind of anti-Putin meeting," he said. He explained that OMON had plucked him from the platform at the Pushkinskaya metro station and put him into the truck.

Maybe he fit the police profile for protesters.

"I'm not going to make it," he said. "Kisses. See you later."

The young man next to me said he was 22 years old and "theoretically" among the organizers of the Dissenters' March. He clammed up when he learned I was a journalist.

We arrived at the police station and were escorted inside. All 12 of us lined up at a desk next to a large jail cell to hand over cigarettes, lighters and other personal effects to a guard. I was the last in line.

The guard did not ask to see anyone's documents. As I approached the table, I saw the others had been put in the cell. One of the detainees asked how long we would be held.

"According to regulations, three hours," the guard answered.

When my turn came, I produced my press pass and British passport, and the guard whistled his superior over to the desk. The officer took me into a back room, where he asked what I was doing at Pushkin Square.

I said I had come to cover the pro-Kremlin Young Guard gathering, which took place at the same time as the Dissenters' March.

He said I would be released on one condition: that I write a statement saying I had no complaints regarding my detention. I did not ask why I had been detained, nor did I ask on what grounds they could keep me in custody should I decline his offer.

I wrote the letter as dictated to me by the officer and was released. But first he insisted on telling me a story about his friend who worked in London and loved it there.