Before the days of package holidays and cheap international travel, many people in Britain had never been to places like Italy or Spain. In Britain, "Risotto" was cooked in a casserole dish in the oven; and to be fair, I suspect this was as much because the proper arborio or carnaroli rice needed to make a proper Italian risotto wasn't available back then. "Spanish Omelette" was cooked with peas, ham and red and green peppers.
This British version is, no doubt, delicious, but it's not a proper Spanish omelette. By this I mean an omelette- as cooked by the Spanish, in Spain. Tortilla de Patatas. The genuine article is made from eggs, potatoes and onions.