Wash and scrub the beetroot under cold running water. Place them in a saucepan with the vinegar, salt and water and bring to the boil. Reduce the heat, cover then pan and simmer for about 1¼ hours until the beetroot is tender. Meanwhile, combine all the marinade ingredients in a bowl and set aside.
Once the beetroot is cooked, drain, place on a cloth and pat dry. Remove the skins with the help of the cloth. Cut into slices, place in the marinade and mix well. Leave for a day before serving. The beetroot will keep for several days in a covered container in the fridge but should be brought to room temperature before serving.