These are the eggs of the large white (the clump of yellowish eggs) and small white (the single whitish eggs to the left and right) butterflies. Both butterflies are known as cabbage whites.
These eggs have been laid on nasturtium leaves: they prefer cabbages and other brassicas, but nasturtiums are a firm favourite food plant of the cabbage whites too.
I gave up growing cabbages in the garden because controlling the caterpillars of these two species of white butterflies on them was impossible. Well, impossible without chemicals. And I took the decision that gardening at home, for me, is gardening for fun and pleasure; it’s not about necessity or earning an income. So, if things won’t grow successfully without plant protection products, I don’t grow them. It’s a very different story when you’re growing a crop to feed your family or earn an income: choices are much harder then.
The photo below was taken about a fortnight later: the caterpillars are literally eating themselves out of house and home!