Heat the oil in a large frying pan and briefly cook the garlic, stirring with a wooden spoon, to start it softening. Add the pork to the pan in a single layer, season and cook for 6 mins each side, until golden and cooked through.
Meanwhile, mix the stock with the thyme and marmalade. Remove the pork from the pan and set aside briefly to rest on a warm plate. Pour off any oil from the pan, then pour in the marmalade mixture and bubble to make a sauce. Return the pork to the pan, coat in the sauce and serve with quick-cooking vegetables like baby potatoes, spinach and peas.