Put your bottles in a moderate oven (180ºC/160ºC fan/gas 4) for 10mins. Return the ketchup mixture to the rinsed-out pan and add the sugar. Bring to the boil, stirring, then boil hard for 8-10mins until thick and syrupy. Decant into your warm bottles, seal and label. Your delicious hedgerow ketchup will keep in the fridge for up to two weeks.