I do love watermelon at this time of year, and tend to buy whole ones as being less extravagant than the boxes of chunks you can buy. Okay, someone has to cut it up, but that's not difficult. But, of course, you end up with boxes full of watermelon chunks in the fridge, and while it's a refreshing dessert, or a delicious salad with feta, but....
And I had run out of "yelm", and although I had the lemons to make more, I didn't have any mint. While plain yelm is delicious, I am also not averse to experimenting. I only made a small amount, to see if it worked.
Rind and juice of 2 lemons
About 300 ml watermelon juice (fill a blender goblet and see how much it makes. Drink whatever is left over!)
25 g citric acid
250 g sugar
About 450 ml boiling water, maybe 500 ml.