I think that's exactly what happened. Thanks for the information as to how this works.

Nothing happened. I think I was being paranoid/cautious as this is something that never happened to me before. Sorry for taking so long to post update.

Thanks for your reply. - Instead of buying a paper ticket, I buy the ticket with the oyster (i.e. the oyster serves as a travel card). - As I understand, only customers with pay as you go oyster cards are required to touch in and out. If you have a travel card in your oyster, you are not required to touch in or out. This is my experience with the DLR, most of stations of which have no turnstiles. My oyster was inspected several times without me touching in or out, and it never posed a problem - as long you have a valid ticket in your oyster and you're not out of the zones in which it's invalid, there won't be a problem. Perhaps I digressed a little in my original post. Let me reiterate what I had wished to ask. The person in charge of the DLR train I was travelling on started inspecting tickets this morning and I failed to show a valid ticket. I pleaded to top up at the next station, which the train was going to stop in about a minute. He let me off at the next station, handing me back my oyster, but left me with the remark that there will be a fine. I wasn't given a penalty fare or anything of the sort. I wondered later whether he might have meant that I'll be receiving a fine through the post (while he didn't take my details at the time, I assume they can be traced as my oyster is registered). What do you think?

No. He handed back the oyster to me when he was letting me off. I topped up and got on the next train. However, my oyster is registered and he saw the balance, my expired travel card etc in his card reader.

I would appreciate if anyone could provide some input as to what will happen in the following case, please. I use the DLR every morning to work, and my travel card runs from Tuesday to Monday. Last week, I thought I'm better off using pay as you go for the week, as I wouldn't be working on (Good) Friday and (Easter) Monday. And so I did. This made me out of sync this week and I went on the train without buying travel card (and without trying to touch in - I got used to not bothering to touch in or out at my local station with my travel card). I was stopped after few stations, and remembered that I didn't buy my travel card as soon as I handed my oyster to the guy. I kind of got shocked, and to be honest I don't even think I explained myself to him. He asked me what station I got and I told him and requested if he could let me top up at the next station. He said 'you do know there will be a fine, right?' twice and I only paid attention as to what that could have meant after he let me off at the next station. He didn't take/ask for any details, but my oyster is registered. What could he have meant? Many thanks in advance.