Strip the redcurrants from their stalks with a fork and add to a preserving pan with the measurement water. Bring to the boil, then cover and simmer gently for 20 minutes, stirring and mashing the fruit from time to time with a fork, until soft.
Leave to cool slightly, then pour into a scalded jelly bag suspended over a large bowl and allow to drip for several hours.
Measure the clear liquid and pour back into the rinsed preserving pan. Weigh 500 g (1 lb) sugar for every 600 ml (1 pint) of liquid, then pour into the preserving pan. Heat gently, stirring from time to time, until the sugar has dissolved.
Bring to the boil, then boil rapidly until setting point is reached (10–20 minutes). Skim with a draining spoon or stir in butter if needed. Leave to cool for 5–10 minutes.
Ladle into warm, dry jars, filling to the very top. Cover with screw-top lids, or with waxed discs and cellophane tops secured with elastic bands. Label and leave to cool.
To serve, pair with scones or spoon onto a cream-topped pavlova with extra strawberries.