Place the bread flour in a large bowl (or the bowl of a stand mixer fitted with a dough hook), add the yeast to one side and the salt and sugar to the other (if salt comes into direct contact with the yeast it can kill it). Stir to combine.
Pour in the olive oil and two thirds of the water, mix together to make a shaggy dough. Add more water gradually until it all comes together into a sticky, but not wet, dough. You may not need to add all of the water or you may need a little more.
Turn the dough out onto an un-floured surface and knead for about 10 minutes until it is smooth and elastic. You can spread a little olive oil on the surface if you find the dough is sticking too much but try to avoid the temptation to add extra flour, the dough does become less sticky as you knead.
If you have a stand mixer you can just go ahead and let that do the kneading for you on a medium speed for 5-10 minutes. The dough is ready when it is smooth and elastic, it should pass the windowpane test. It will become less sticky as you knead but should still feel slightly tacky.
Place the ball of dough into a lightly oiled bowl and cover. Leave it to rise until it is doubled in size, about 1-2 hours in a warm spot or overnight in the fridge.
Once the dough has risen, knock it back then roll it out on a lightly floured surface into a rectangle approx. 30 x 45cm. Spread the pesto evenly all over the dough, leaving a 2cm border around the edge.
Starting at the long edge closest to you, roll the dough up tightly but gently, like a swiss roll, into a log.
Line a baking sheet with baking parchment or sprinkle it with semolina. Transfer the roll of dough to the baking sheet and, using a sharp knife or bench scraper, cut the roll in half lengthwise.
Turn the two halves so that the cut side is facing up then lay one over the other so that they make an X shape.
Twist them together by laying one side over the other, keeping the cut side up, until all of the dough is twisted and you are left with a braid. Loop the braid round into a wreath shape and pinch the ends together.
Loosely cover and leave to rise for about 45 minutes until it is puffy and increased in size. The dough should spring back slowly if you gently press it with a finger, if it springs back quickly then it needs a little longer.
Meanwhile, preheat the oven to 200°C/180°C fan/400°F/gas mark 6. You may find that while the dough is rising you get lots of oil from the pesto puddling on the baking sheet, if this happens, gently blot it up with some kitchen roll.
When the dough has proved, place in the centre of the oven and bake for 25-35 minutes until it is golden brown and baked through. The internal temperature should reach at least 90°C/194°F on a probe thermometer.
If it starts to colour too quickly, cover loosely with some tin foil. Once baked transfer to a wire rack to cool.