I suppose the best word to describe it was ubiquitous.
In an age before people cared about the quality of beer Red Barrel was the drink of choice for millions of peope and it was shite.
Flat,weak and gassy with no head.
Perhaps the most well known beer of the 60s and 70s, the much maligned Watneys Red Barrel, can trace its origins back to the 30s; in fact Watneys claimed 1931. Red Barrel was originally developed as an export beer that could be transported for long distances by sea.

Red Barrel, like all keg bitter, was filtered, to remove the yeast. It was then pasteurised and carbon dioxide was added. The "keg" was linked to a tank of carbon dioxide which effectively forced the beer up from the cellar. There was no need for the traditional long-handled beer pump. Keg was usually served chilled and was fizzy, with froth on the top.

Red Barrel was tentatively trialled at the East Sheen Lawn Tennis Club where Watneys' Master Brewer, Bert Hussey, was a member. He was convinced that once sampled it would be instantly popular. By the early sixties, Watneys were able to claim that it was the country's most popular keg bitter. It was also the first.

Red Barrel today is regarded with distain; in the 60s it was a premium product. Watneys negotiated a contract with BEA for Red Barrel to be supplied to passengers. Given that air travel, especially on scheduled flights, was still a privilege of the few, this must have been quite an achievement for Watneys and must say something about the quality image that the brand then had. Watneys were also able to sell Red Barrel at all bars on the new luxury liner, the QE2.