Preheat oven to a 180°C/160°C fan forced.

Lightly grease a 20x30cm baking tin.

Stir together walnuts, cinnamon and caster sugar.

Spray 1 sheet of pastry with oil, fold crosswise in half.

Place in pan.

Repeat with 3 more sheets.

Spoon over half the walnut mixture.

Repeat pastry process with 4 more sheets.

Spoon over remaining walnut mixture.

Spray and add remaining 4 sheets.

Spray top.

Using the tip of a sharp knife, score top layer into diamonds.

Bake 30 minutes.

Stir sugar, 2 3 cup water, cinnamon and lemon juice in a small saucepan over low heat until sugar dissolves.

Bring to the boil; reduce heat.

Simmer 5 minutes.

Pour evenly over hot pastry.

While still warm, cut layer through into diamonds.