To make the lemonade, mix the lemon and lime juice, raspberry syrup and caster sugar in a jug. Stir to dissolve the sugar. Add 575ml/1 pint water and plenty of ice.

Put the potatoes and carrots in a large saucepan, cover with water until it rises just 1cm/½in above the vegetables and place a lid on top. Bring to the boil over a high heat.