Rinse, dry and pick over the cherries discarding any that are bruised or imperfect. Leave the stalks on. In a generous-sized, non-reactive saucepan, stir together the sugar, red-wine vinegar, garlic and peppercorns. Bring to a boil and cook for around 3 minutes.
Have handy a couple of sterilised jars with the ability to hold approximately 1litre (13/4 pints). Pack the cherries into the sterilised jars. Pour the hot syrup over then cover and seal well.
Leave to sit for a month or two in a cool, dark place before eating. If properly sealed, the cherries will keep refrigerated for up to a year.