Cut the steak into cubes. For the marinade, peel and crush the garlic. Combine the port with the vinegar, add the garlic and thyme, bring to the boil. Reduce by half then add the olive oil.
Reserve a little marinade for serving.
Place the steak cubes in the marinade, then thread them on the skewers. Cook 7–8 minutes over high heat depending on how you like your meat cooked, seas