Roll bases out on a clean dry surface sprinkled with a little flour, then place on pizza trays. Use a fork to prick the dough all over to prevent large air bubbles from forming. Spread desired amount of beetroot and horseradish over the base leaving a thin border around the edge to give it that authentic pizzeria look.
Mash mackerel with a fork in a bowl and add a squeeze of lemon, mix well and spread over the pizza. Tear bocconcini and place over the base.
Cook pizza, in a preheated 180°C oven, or in a pizza oven for approx 15-20 mins. Remove and sprinkle fresh rocket over the pizza, slice and serve!