Method

1. Strain the yoghurt: Use a muslin cloth (or a clean, unused Chux) and put the yoghurt into the middle of the cloth.  Tie up each corner diagonally to make a kind of bag.  Thread a wooden mixing spoon through these tied corners (or any other type of large mixing spoon) and suspend the bag over a deep bowl to strain the yoghurt.  Leave it to strain for at least 6 hours but preferably overnight in the fridge.  You need it to be similar to the consistency of labneh (thick yoghurt that has been very well strained).
2. Strain the cucumber: Wash the cucumber well and either leave the skin on or peel some of the skin off.  Grate it using the large holes of a box grater.  Salt it to taste.  Place the grated cucumber in a strainer over a bowl and, again strain for at least 6 hours, preferably overnight in the fridge.
3. Place strained yoghurt and cucumber in a bowl and mix with a spoon till combined.
4. To this mixture add the fresh garlic, white wine vinegar, teaspoon salt and extra virgin olive oil.
5. Mix well by hand with a spoon.
6. Taste and adjust by adding more garlic and/or vinegar (but be careful not to add too much) and/or salt and/or olive oil.