Dice the chicken thighs into small chunks. Add to a large bowl.
Grate the garlic and chilli into the bowl. Add 3 teaspoons of oregano, the zest of a lemon, 3 tablespoons of yogurt and salt and pepper. Rub together and cover with clingfilm (plastic wrap). Put in the fridge to marinade for 15 minutes.
Tzatziki time. Pour the rest of the yogurt into another bowl. Chuck in a finely chopped small bunch of mint, the juice of the lemon and a grated cucumber (squeeze out the grated cucumber to remove any excess liquid). Season well and mix it all together.
Tomato salsa time. Deseed and finely chop the tomatoes. Add to a bowl with 2–3 teaspoons of dried oregano, salt, pepper and olive oil.
Finely chop the lettuce.
Put a griddle pan over a medium–high heat. Once it is hot, add your chicken chunks. They’ll need 3 minutes on each side.
Warm the pittas in a toaster or in the microwave.
Assemble the gyros by adding the chicken, lettuce, salsa and tzatziki to the pittas and rolling them up. Tuck in!