Go pick half a dozen full elderflower heads ideally on a sunny day when they are most fragrant. They are all over the place at this time of year. Elderflowers tend to be home to small insects so give them a gentle shake to dislodge any tenants.
1. Put the hot water and sugar into a large container (a spotlessly clean bucket is good) and stir until the sugar dissolves, then top up with cold water so you have 6 litres of liquid in total.
2. Add the lemon juice and zest, the vinegar and the ower heads and stir gently.
3. Cover with clean muslin and leave to ferment in a cool, airy place for a couple of days. Take a look at the brew at this point, and if it’s not becoming a little foamy and obviously beginning to ferment, add a pinch of yeast.
4. Leave the mixture to ferment, again covered with muslin, for a further four days. Strain the liquid through a sieve lined with muslin and decant into sterilised strong glass bottles with champagne stoppers (available from home-brewing suppliers) or Grolsch-style stoppers, or sterilized screw-top plastic bottles (a good deal of pressure can build up inside as the fermenting brew produces carbon dioxide, so strong bottles and seals are essential).
5. Seal and leave to ferment in the bottles for at least a week before serving, chilled. The champagne should keep in the bottles for several months. Store in a cool, dry place.