The most uniquely embarrassing thing I have ever witnessed.

Ever ruined somebody's morning just by being there?

I used to work at a hospital. One day as I was walking into one of the hospital buildings I saw a medical student make a faux pas as he passed a nice looking girl answering a phonecall.

As she said "hello" into the phone, he thought she was talking to him and chirped "hello" back. She ignored him and, realising his mistake, he went bright red.

These things happen, but it's worse when there's a witness. He glanced around and spotted me, witnessing, and his desire to flee instantly doubled. Avoiding eye contact, he hurried into the building. Sadly for him I was going in the same direction.

He reached a doorway in the near distance and, being British, he checked to see if he needed to hold the door open for anybody behind him. And there I was, following him like a bad smell. This presented him with a quandary: should he politely hold the door open, thereby acknowledging my presence, or should he simply plough on through? Being a good sort, he held it open. This turned out to be a mistake.

The student's social radar was on the blink after the incident outside, and his faintly frantic escape velocity had put so much distance between us that I was now well behind that invisible line at which door-holding seems appropriate. Frankly, I was miles away.

Most of us have held a door open for too long at some time or another. It makes you feel a bit silly but you can generally sort it out by exchanging a spot of small talk. He didn't want to talk, and so he faced an excruciating 30 second wait during which the mild doorway error was figuratively rubbed in his face.

I tried to help by breaking into one of those pointless trots, but it didn't help. He became increasingly fidgety as I approached until, by the time I reached the door, he was fully flustered, causing him to let go a split second too early. The door swung into my face as he hurtled off down the corridor.

Holding a door open for too long might make you feel daft; shutting it in someone’s face is generally considered to be worse. It's unusual to achieve both at the same time.

It could have ended there. The student's speeding legs were whisking him away from me - the sole witness to his cumulative clumsiness - so fast that by the time I reached the end of the corridor, he was rushing up a flight of stairs and was almost out of sight. And I was happy for him. He was finally fleeing the scene, never to see me again. In a few moments the whole sorry business would be behind him and he could get on with the rest of his day.

I glanced up at him briefly. He fell over.

There was a resounding thump as knee hit stone in the hollow hallway. I hoped he would glance round so I could offer a friendly smile, or an empathetic shrug, something to let him know that it was fine, that it happens to the best of us, that I was on his side. But his eyes were fixed ahead. He stood up, took off up the steps, and was gone forever.

It was at this point that I realised I had witnessed something unique. It was a very specific type of domino effect: an insignificant blunder with a girl on a phone, leading to a subtle misjudgement in doorway etiquette, leading to a bigger doorway error which, in turn, led to an actual fall on a staircase. All within 90 seconds and all in front of the same stranger. Something so minor, yet stretched to the point that it became genuinely ridiculous, a series of tiny embarrassments that meant nothing by themselves but, collectively, added up to a train wreck. I don't think I'll ever see anything like it again.

Which is a shame, because it was very entertaining.