Put the flour, salt, sugar, yeast and butter into a large bowl and mix together, then slowly add the water until all the flour has been incorporated (you might not need all of it).

Tip out onto a lightly floured surface and, using your fingers and palms, knead for 5 minutes.

Put the bread back in the bowl and leave to rest for 1 hour.

Line a baking tray.

Add the grapes and sultanas to the dough and mix in well, then shape into a ball, flatten slightly using your hand and dust the top with flour.

Put onto the baking tray and leave to rise for 1 hour.

Preheat the oven to 200°C/400°F/gas mark 6.

Cut a square in the top of the dough and bake for 25 minutes.

Transfer to a wire rack to cool.