Prep the crust: Blitz the biscuits in a food processor until they resemble fine sand — no large chunks should remain. Stir in the melted butter and 1 tbsp sugar. Press the mixture firmly into a 20cm springform tin lined with parchment. Bake at 160°C for 8 minutes; the crust should look dry and smell toasty. Set aside to cool.

Whip the cream cheese: In a large bowl, beat the softened cream cheese with an electric mixer until it feels silky and looks glossy — about 2 minutes. Scrape the sides well; a smooth base prevents a grainy texture later.

Add the sugar and eggs: Pour in the 150g sugar and beat until the mixture feels light and airy, about 1 minute. Add the eggs one at a time, mixing on low after each until just combined — over-mixing here introduces air bubbles that cause cracks.

Finish the filling: Gently stir in the double cream, lemon zest, lemon juice, vanilla, and flour. The batter should be thick, pale yellow, and smell sharply of lemon. Fold in 200g blueberries with a spatula — you want them evenly dispersed, not squashed.

Bake the cheesecake: Pour the filling over the cooled crust and spread it evenly. Bake at 160°C for 35-40 minutes. The edges should look set and slightly puffed, while the centre will jiggle like a wobbling jelly when you gently shake the tin.

Cool and set: Turn off the oven and leave the cheesecake inside with the door ajar for 30 minutes — this gentle cooling prevents a dramatic crack. Transfer to a wire rack until it reaches room temperature, then refrigerate for at least 4 hours, ideally overnight.

Top and serve: Scatter the reserved 50g blueberries over the set cheesecake just before serving. Slice with a hot, dry knife for clean cuts.