Put a saucer in the freezer. Tip the syrupy apricots into a preserving pan or a large, wide-based pan (the wider and more open the pan, the faster the jam will be ready, so a preserving pan is ideal). Add the lemon juice and place over a gentle heat. Once any last bits of sugar have melted, turn up the heat and boil for 15 mins. Turn off the heat and spoon a little hot syrupy jam onto the cold saucer. Once cool, push the jam with your finger. If it wrinkles a little, it’s ready and has reached setting point. If it is too runny to wrinkle, return the pan to the heat and boil in stages of 2-3 mins, removing the pan from the heat each time you do the saucer check, until the jam wrinkles.