By which I mean I added boiling water and sugar, let them cool, and stuck some yeast in (oddly it was champagne yeast, because for some reason that was what the shop I went to had). Then when it had bubbled for a few days, I thought I should probably do something with it, so I took the elderberries out and stuck the liquid in a demijohn. There wasn't enough to fill it properly, so not having any applejuice to hand, I topped it up with elderflower squash, reasoning that this is basically flavoured sugar-water, so should ferment as well as anything. It remains to be seen what will happen.
Yesterday, we had dinner with members of my family, and my sister, her partner, and Pp's dad, who have all, in the past, dabbled in wine-making, united to tell me that wine-making was a Slippery Slope and before long I would have a house jammed to the rafters with bottles and bottles and bottles of undrinkable plonk. They were filled with terrible stories of exploding bottles and acres of demijohns.
This seemed odd. I only own one demijohn, and I don't even have any more yeast. I make jellies and things, and nobody has ever warned me that jellification is a Slippery Slope. I make cakes, too, but it had not previously occurred to me that I might suddenly get carried away and end up with a house packed with the things (although, note to self, if I do this, fruitcake is probably the way to go. It would keep and stack well.) Maybe the key thing is not to sample the product too soon.