Cut the pork fillet into small cubes and place in a bowl. Add the chopped rosemary, garlic, lemon zest, olive oil and season well with pepper and salt. Mix together well, cover with cling film, and leave to marinate for 4 hours, or overnight. Meanwhile you can start preparing the salad too, as this is also best served chilled. Place all the ingredients in a bowl and mix together. Season well with salt and pepper, and chill till ready to serve. When the meat is ready to use, take it out of the fridge and thread onto the soaked wooden skewers. Previously soaking the skewers in water will stop them from burning. Next, heat a large griddle pan and put in the pork skewers. Cook them quickly on all sides, turning every minute or so. You shouldn’t need to cook the pork fillet for more than a few minutes. Serve two pork skewers per person, with a good portion of the crunchy apple and walnut rice salad.