This helps the sugar to start dissolving so you don’t run the risk of over-cooking the fruit when you actually begin to make the jam.

The next morning, give everything a quick stir, then set aside again until you are ready to start cooking.

2)Before you start, put a small saucer in the freezer.

Tip the berries, scraping out all juices and any undissolved sugar, 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 really ideal).

Stir in the lemon juice, then collect all the pips and secure them inside a tea-leaf strainer or piece of muslin before adding to the pan, too (cooking the pips along with the fruit extracts the pectin they contain, helping your jam to set).

3)Start the berries over a low heat until all the sugar is completely dissolved, then bring to the boil and simmer for 5 mins.

Turn off the heat and spoon a little hot syrupy jam onto the chilled 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 2-3 minute stages, removing the pan from the heat each time you do the saucer check, until the jam wrinkles.

4)Skim off any excess scum, then stir in the knob of butter, if you want – this will help to dissolve any remaining scum.

Leave the jam for 15 mins before ladling into sterilised jars  this allows the fruit to settle so it doesn’t sink to the bottom.

The jam will keep in a cool, dark place for at least 6 months.

Refrigerate jars once opened.