Prepare the pears – Peel, core, and slice the pears evenly. Place them in the baking dish, toss gently with lemon juice and caster sugar, and spread them out in an even layer so they soften uniformly as they bake.

Make the crumble topping – Put the plain flour and cold butter into a bowl. Rub the butter into the flour using your fingertips until the mixture resembles coarse breadcrumbs. Work lightly to keep the topping crumbly rather than doughy.

Add the sugar – Stir the light brown sugar through the crumble mixture so it is evenly distributed. This helps the topping caramelise slightly during baking.

Assemble the crumble – Sprinkle the crumble topping evenly over the pears, covering the fruit without pressing it down. A loose topping gives the best crisp texture.

Bake until golden – Place the dish in the oven and bake until the pears are soft and bubbling around the edges and the crumble is golden and crisp on top.

Rest briefly before serving – Let the crumble stand for a few minutes after baking. This allows the juices to thicken slightly and makes serving easier.