I decided to take the plunge and pick a cob today. This is the one I checked for ripeness the other day and you can now see how much the top of the cob is undeveloped. After I'd fully opened it up and squeezed one of the kernels closer to the base of the cob and the liquid that emerged was milky.
I boiled it for 3 minutes and it was lovely and sweet. However the kernels were quite small. They look quite plump but they are actually quite shallow so when you bite into it you don't get a satisfying amount of corn to munch on. But I'm still really pleased that I've managed to grow a new vegetable and it was edible! Most of my corn plants have double cobs, so we've still got a few more to enjoy!