Place the 4 lemons in a saucepan and cover with water. Bring to the boil and then simmer for 1 hour.
Pre-heat the oven to 180°C /160°C fan/gas mark 4 and line and grease a 2lb loaf tin.
Remove the lemons from the saucepan. Cut in half to remove and discard the pips.
Place the lemons in a blender and blitz until smooth. Set aside for a moment.
Beat the eggs and sugar in a large mixing bowl (or food mixeuntil pale and thick.
Mix in the pureed lemons.
Add the cornmeal, ground almonds, baking powder, thyme leaves and salt. Mix until thoroughly incorporated.
Pour the batter in the prepared loaf tin and bake for around 45-50 minutes until an inserted toothpick comes out clean.
Remove the cake from the oven and prepare a honey glaze.
Melting the honey with 2 tablespoons water in a small saucepan. Brush the glaze over the cake whilst it is still in its tin.
Let the cake cool in the cake tin before removing and drizzling with lemon icing.
Make the lemon icing by stirring together the icing sugar and the juice of ½ lemon until thick but still just pourable.