Preheat oven to 356F/180C, and grease a 1 liter loaf tin.
In a small sauce pan, bring the water to a boil. Add two Earl Grey tea bags into the water and allow to infuse for half an hour. Then, squeeze well the tea bags and discard.
In a bowl, mix together flour, baking powder and a generous pinch of salt. Set aside until needed.
In the bowl of a stand mixer add the lemon zest, brown sugar, caster sugar, and butter. Beat until well combined.
Add the eggs, one at a time, incorporating well between additions.
Add lemon juice, the prepared Earl Grey tea, honey and olive oil, and continue to mix until well combined, scraping the bottom of the mixer if necessary.
Stop the mixer and slowly add in the flour mixture, lightly stirring until just combined.
Pour half the cake mixture into the prepared cake tin and top with blueberries. Then, evenly pour over the remaining cake mixture.
Bake for about 30 mins, or until cake is golden on top and a toothpick inserted in the center comes back clean. If the top is browning too quickly, cover with aluminium foil towards the end of baking time.
Remove from the oven and allow to cool completely before removing the cake from the tin.
In the meantime prepare the glaze. In a small saucepan, heat the sugar, lemon juice and water over very low heat. Once the sugar has dissolved, remove from the heat and allow to cool slightly. If you prefer a runny glaze, just add a little more lemon juice.
Spread the glaze over the top of the cake and decorate with fresh blueberries.
Serve immediately, and store in an air-tight container in the fridge for up to 4 days.