Preheat the oven to 160°C / Gas Mark 3 / 325°F.
Grease a loaf tin and line it with a strip of greaseproof paper, wide enough to cover the length of the pan and up both sides with about an inch or two overhang to act as handle.
In a large bowl, mix together the flour, baking powder, bicarbonate of soda and salt. Set aside. Zest the lemons, reserving 2 tsps for the glaze. Combine the zest with the sugar in a bowl and massage them together for at least 1 minute so that the oils are released. Add the eggs and whisk thoroughly. Add the yoghurt, oil, juice from 2 of the lemons and vanilla and whisk until smooth. Then mix in the dry ingredients until thoroughly combined.
Pour the batter into the pan and tap firmly 2 or 3 times to expel any large air bubbles. Cook in the oven for 30 minutes. If necessary cover the cake with foil and return the cake to the oven for a further 10-20 minutes or until a skewer comes out clean. When cooked remove from the oven and carefully run a blunt knife around the cake to loosen it from the sides. Allow the cake to cool completely before lifting it out of the tin.
To make the glaze beat the icing sugar, milk, lemon zest and lemon curd together until combined and then drizzle over the cake.
It's ready to be enjoyed right away but if you are baking ahead we recommend storing it in the fridge overnight and bringing it to room temperature before serving.