Preheat the oven to fan 180C/ conventional 200C/gas 6. Wash the potatoes, but don’t bother to peel them. Cut into thickish slices then cook in boiling water for 6-8 minutes until almost tender; drain. Slice the tomatoes to the same thickness. Chop the garlic, then strip the rosemary from its stalks and chop the leaves fairly finely.
Drizzle a little olive oil in the base of a shallow ovenproof dish wide enough to take the chops in one layer. Arrange rows of potatoes and tomatoes across the dish, seasoning with salt and pepper as you go and sprinkling with half the rosemary and all the garlic.
Drizzle a couple more tablespoons of olive oil over the vegetables and bake for 15 minutes, then sit the pork on top, season and sprinkle with the remaining rosemary. Return to the oven for 35-45 minutes, until the pork and potatoes are tender.