Sterilise the jars you'll be using to store the jam. Choose glass jars with an airtight, metal lid and ensure they have been washed by hand in hot soapy water then rinsed well. Check that the metal lids do not have rubber inserts – if they do, allow them to air dry, instead of placing in the oven. Preheat the oven to 270 F (130 C) and place the jars in the oven for 15-20 minutes. Keep the jars warm. See Note 5.

Place two small saucers or plates in the freezer. See Note 6.

Gently wash the raspberries in a colander. Turn them stem side down onto some paper towel to allow them to dry. Add the raspberries, sugar and lemon juice to a large saucepan and mix well with a long-handled wooden spoon.

Turn the heat on low and stir until the sugar dissolves. (This can take 5-8 minutes) If sugar crystals get caught on the side of the saucepan, scrape down with a spatula.

Once the sugar is dissolved, increase the heat to a rolling boil. Boil for 5 minutes, stirring frequently. After 5 minutes, begin to check for the setting point. Your jam will likely take between 5-8 minutes, but it will depend on the width of your saucepan and how rapidly the jam is boiling.

Turn off heat and spoon a little of the jam onto one of your chilled saucers. Let it stand for 30 seconds to cool, and then run your finger through it. If it wrinkles, even slightly, it is ready. If it is still quite liquid, put it back on the heat and boil for a further 1-2 minutes, and retest until ready. Alternatively, you could use a candy thermometer. Setting point is reached when the thermometer reaches 220 F (105 C).

Skim any scum off the top of the jam with a spoon.

Allow the jam to sit for 5 minutes to allow the fruit to disperse evenly.

Carefully ladle your jam into your hot jars and put the lids on immediately. Allow the jam to cool completely. Wipe the jars to remove any spills, and store the jam in a cool, dark place.