Hull strawberries - halve or quarter large ones.
Add strawberries to your preserving pan and cook on a gentle heat for 5 to 10 minutes to soften the fruit. Shake the pan a couple of times to prevent fruit sticking to the pan.
Add the sugar, stirring gently to dissolve it.
Check the sugar has completely dissolved before increasing the heat to medium.
Add lemon juice and stir.
Bring to a gentle rolling boil and cook for 12 minutes and test for setting point.
Setting point is reached when the jam thermometer reaches 104℃ or 220F.
Alternatively, use the wrinkle test: Remove your pan from the heat and test for setting point by dropping a little jam onto a cold saucer, return to the fridge and leave to cool for a minute. Push the jam gently with your fingertip, if the jam crinkles, setting point has been reached. If not, reboil for a couple of minutes and repeat until setting point is reached.
Leave to settle for about 10 minutes before pouring into warm, sterilised jars and seal.
Store in a cool, dry place out of the sunlight and use within 12 months.