Dissolve yeast and sugar in 125ml warm water and set aside, covered, for 15 minutes. Dissolve salt in the remaining 250ml warm water.
In a large mixing bowl, add flour and make a well in the centre. Add yeast mixture and salt water. Knead with hands for 10 minutes in the bowl. Add olive oil and continue to knead until all oil is absorbed. Shape into a ball in the bowl, cover and place in a warm area to rise until doubled in volume, approximately 1 1/2 to 2 hours. Punch down the dough and knead for 5 minutes more.
Preheat oven to 180 C / Gas 4 and lightly grease some baking trays.
Take pieces of dough slightly larger than an egg and roll out on a floured surface to 5mm thick. (For larger or smaller pitta bread pieces, take more or less dough). Prick the bread with a fork in several places.
Place on baking trays and bake in preheated oven on the lowest oven rack for 2-3 minutes, then turn the pittas over and bake for another 2-3 minutes. Remove from oven and place on a tray covered with a clean tea towel, with another clean towel on top. When thoroughly cooled, pittas can be stored in plastic bags in the refrigerator or frozen.
Before using, brown in a lightly oiled frying pan for a few minutes until browned on both sides.