Pick 10 large elderflower heads.
Gently shake them to make sure you get any insects or bugs and leave them for an hour on a tray (if there are any more bugs, they will crawl away)
Cut out the green stems
Prepare zest from the two lemons
Put the elderflowers and lemon zest into a plastic container
Cover with boiling water (I boil my water in a kettle and then place my plastic bowl directly on a scales, making sure they are set to zero and pour out the 650ml of boiling water)
Cover and leave to infuse overnight or for at least 12 hours
The next day, pour the infused elderflower water over a fine sieve (or a sieve lined with a musln cloth)
Add the elderflower water to a large saucepan with the sugar and juice from the two lemons
Heat very gently and make sure the mixture doesn't boil.
When all sugar is dissolved, bring to simmering point and continue to simmer for a few minutes.
Pour into a suitable bottle, seal and leave to cool down
Use straight away or keep for a few weeks in the fridge or somewhere cold.