Preheat oven to 180c.

Place rhubarb into a square or ovel oven proof dish. Sprinkle with the caster sugar and water. Roast for around 10-12 minutes.

In the meantime, in a bowl rub the flour with the butter until it resembles breadcrumbs. Mix in the demerara sugar.

Remove rhubarb from oven and sprinkle with the ginger. Mix well.

Top the rhubarb with the crumble mixture. Transfer to oven for 35-45 minutes or until the top is golden brown and edges are bubbling.

Allow to cool for 30 minutes before serving. Serve with double cream