Prepare 2 or 3 1lb-jars and lids by washing well in warm soapy water and rinsing thoroughly. Bath them in a pan of boiling water for a while. Dry the jars.
Well wash, remove stems and pat them dry with a clean kitchen towel. Slice strawberries. Peel the lemon and thinly shred lemon rind. Drop in squeezed lemon.
In a big non aluminum pan, add the prepared fruits and the preserving sugar and combine them briefly. Cover and refrigerate 3 to 4 hours. You would see a lot of liquid coming off the strawberries. Heat the strawberry mixture to boiling over medium heat, and allow it to boil for about 5 minutes, stirring frequently. Ladle marmalade into still very warm jars to prevent the jars from cracking when the hot filling is added. Wipe jar rims clean and seal with lids and bands. Store marmalade in a cool and dry place. After opening jar, store marmalade in the refrigerator.