Agree with Cougie that it sounds more like a minor wobble and not The Actual Wall. Unless when you say you carried on, you mean it was more of a grim death shuffle rather than an actual run?
Anyhoo, yes, congratulations. Sounds like you did pretty well in what I'm assuming was your first marathon. My suggestions for future marathons would be to get in at least one 22+ mile run in training, and to practice more with gels to see which ones give you the best boost. (Rather than just taking what's on offer at feed stations, which might not be what you want or exactly when you want it.) Caffeine laced ones tend to be pretty good for giving you a kick up the bum. Then you can make sure you've got a couple stashed in a pocket for just before the 22 mile point.
Marathoners often make a huge deal out of The Wall but remember ultra runners do 50 mile, 100 mile and even longer races without running out of steam at the 20 mile point so sometimes I think the marathon wall is often psychological rather than physical. Like, if everyone tells you to expect it and you're thinking about it, it's more likely to happen.