I found it needed a lot more sugar than this - and I mean a LOT. Maybe it's casue I was looking for something much sweeter than he had in mind, or something resembling the ginger beer you get in shops. Either way, I used all three lemons, and a mysterious unmeasured quantity of grated ginger. That's how I roll in the kitchen.
140g/5oz fresh ginger
4 tablespoons muscovado sugar
2 to 3 lemons
1 litre/1¾ pints soda water or sparkling mineral water
sprigs of fresh mint
First of all you need to grate your ginger on a coarse cheese grater – you can leave the skin on if you like. Put the ginger with its pulpy juice into a bowl and sprinkle in your muscovado sugar. Remove the rind from 2 of your lemons with a vegetable peeler, add to the bowl, and slightly bash and squash with something heavy like a pestle or a rolling-pin. Just do this for 10 seconds, to mix up all the flavours. Squeeze the juice from all 3 lemons and add most of it to the bowl. Pour in your fizzy water or soda water. Allow to sit for 10 minutes and then taste. You may feel that the lemons are slightly too sour, therefore add a little more sugar; if it's slightly too sweet, add a little more lemon juice. To be honest, these amounts are always a little variable so just follow your own taste. Pass the ginger beer through a coarse sieve into a large jug and add lots of ice and some sprigs of mint."