I happened across an amusing interaction at Victoria on a sunny weekday morning in May. It was between a luggage-laden tourist and a member of tube staff. I was too far away to hear a word they uttered, yet I knew precisely what was happening.
At the entry/exit of the District line, the barriers are parallel. So as you come out, the entry ones are straight in front of you. It was here that I witnessed a cheery member of TFL staff fishing around inside the workings of one of the barriers, while the woman stood by, slightly embarrassed, with a couple of large suitcases. After a second or two he handed her an Oyster card, while miming the action of placing the card on to the reader.
She had clearly stuffed the Oyster card into the paper ticket slot and this kind gentleman had fished it out for her. As a seasoned Londoner I couldn't quite believe that an Oyster card would even fit inside, but it seems she was very much successful in this endeavour.
They both found the situation highly amusing, as did I, and I was left with the curious conclusion that this cannot have been an isolated incident. In fact I'm surprised I don't see it more often.
A few seconds earlier or later, and I would have missed the whole thing.