It took me quite a while to find R. White's Lemonade after I first heard of it. It's a UK beverage, but can be found in specialty stores in rare locations. R. White's Lemonade dates back to 1845 when Robert and Matthew White started making their lemonade in Camberwell. Camberwell is a small area of greater London just south of the City of London. R.White & Sons became incorporated in 1894, but has been under the Britvic corporation since the late 1980's. In the 1970's they made other flavors which don't exist anymore. However, they still have a Raspberry Lemonade and a Pear & Elderflower Lemonade.
In the 1970's they used the slogan, "Secret Lemonade Drinker". The advertising featured a song by Ross McManus and his son, Declan McManus. Declan would later become known as Elvis Costello.
This doesn't have the overly sugary flavor you'd expect from a lemon soda or lemonade beverage in the U.S. They use lemon concentrate in making this drink and although it has sweeteners in it, you might think it was closer to lemon juice used in baking than the soda's people in North America might expect. They used to make their lemonade with sugar, but now include aspartame alone with sugar in the drink. I'd go so far as to call it a bit bitter. Drinking it alone is probably not as good as if you were to pair it with something salty which I think would make it taste sweeter.