2) Preheat the oven to 200C/Gas 6.
3) Sift together the flour, baking powder, bicarbonate of soda, remaining 2 tbsp sugar and salt in a medium bowl. Add the double cream and mix until just combined. Place the mixture in an ungreased 20cm square pan and bake until golden, 18 to 20 minutes.
4) Remove the shortcake from the pan and place on a rack to cool slightly. Cut into 6 pieces and split each piece in half horizontally.
5) Make the whipped cream: using a mixer or electric beaters, beat the cream, sugar, vanilla and lemon zest in a medium bowl until soft peaks form, about 1 1/2 to 2 minutes. Set aside.
6) Spoon some of the strawberries with their juice onto each shortcake bottom. Top with a generous dollop of whipped cream and then the shortcake top. Spoon more strawberries over the top and serve.