Peel the mangoes and cut as much flesh as possible from the stone. Cut the flesh into small chunks and put it in a bowl with the sugar, lime rind and lime juice. Stir, cover and leave overnight in the fridge to draw out the juice. Purée until smooth and, if necessary, pass through a sieve to extract the very pulpy and stringy bits. Taste for sweetness and add extra caster sugar,
Pour the purée into a bowl or container that has a lid. Put the lid on and put it in the freezer. After an hour give the mixture an energetic whisk with a hand whisk or electric mixer. Put it back in the freezer and then whisk again after another couple of hours. When the sorbet is nearly firm, give one last whisk and put it back in the freezer to set.
Alternatively, pour into your ice cream machine and churn, following the manufacturer’s instructions.