Cabbage White Eggs?
I was putting some tomato plants into a couple of bags for our Son in Law (Luke, Ruby's Father) to pick them up and lifted up one of the Brussel Sprout plant leaves which was drooping a little.
I found these small, very neat, eggs on the back of the leaf. As far as I can determine they are of the Cabbage White butterfly.
I like butterflies but I don't want to lose my Christmas Brussels to them!