I had my first all-Brettanomyces beer earlier this month: Evil Twin’s Femme Fatale, which was on keg at the Cask in Clerkenwell, and is apparently meant to be a “Brett IPA”. It was … “interesting”, but perhaps only if you believe it’s interesting to drink something that tastes like essence of sweaty old leather sandals.

All-Brett beers have been popular for several years now in the US, of course. But the point about Brett, I think, is that, rather like hops, it’s meant to be used as a “spice” in beer, not the only audible ingredient. An all-Brett beer is an orchestra where the timpani is so amplified, you can’t hear anything else. If you want to use Brett – and it’s been an influence in brewing for many centuries, albeit a mostly unrecognised one – then it needs to be used judicially, particularly as its effects, the aromas and flavours it gives to beer, vary considerably depending on just how great a role Brettanomyces yeasts have been given. A subtle suggestion of something funky can be fine in a strong, complex ale. Being battered about the nostrils with all the aromas of a rugby team changing-room after a tough match on a hot day – not so much.

(Incidentally, the next person who writes that Brett gives a “horseblanket” aroma to beers will be poked with red-hot branding irons: I doubt more than one in five hundred beer drinkers knows what a horse blanket smells like, and I bet very, very few beer writers who steal that description from Michael Jackson have ever sniffed a horse blanket either.)

My wrestle with Femme Fatale (which I left sitting on the bar after less than a third of a pint) was a good limbering-up, however, for a beer Ed Wray of the Old Dairy brewery in Kent sent me more than a year ago, his “homage” to Colne Spring Ale. CSA is another legendary beer, vanished many years ago yet still talked about. It was made by Benskin’s of Watford, the biggest brewery Hertfordshire produced; named after the River Colne, which flows through Watford on its way to the Thames; and famous for being one of the strongest beers in Britain until it finally vanished in 1970.

There are a host of stories about Colne Spring Ale and its strength: it was a highly regarded brew 120 years ago, when Alfred Barnard, the great Victorian beer and whisky journalist, visited Benskin’s brewery. Of CSA he wrote:

“Never was there a more delicious beverage that this … full-flavoured, soft, creamy, yet vigorous.”

Some 60 years later, CSA entered the life of Bob Hawke, the Australian prime minister best known for drinking two and a half pints of beer in 12 seconds while he was at Oxford University in the early 1950s (this is often said to have been done using a yard of ale, but in fact Hawke seems to have been drinking from a “sconce pot” – the tankard reserved for offenders against college etiquette. The account is from Hawke’s 1979 biography, by John Hurst: “Frearson” is Keith Frearson, later an economics professor at Monash University in Melbourne.

At Cambridge Frearson was one of the instigators of a practical joke against Australians who boasted they couldn’t get drunk on English ale. Hawke was one of the victims. Frearson, Salter and John Smith, a dentist, had discovered a particularly potent brew, Benskins’ Colne Spring Ale, priced at half a crown a bottle. It was so strong that publicans seldom sold large quantities to their English customers, who generally had a milder taste. But Australians, confident that they could hold their liquor, were fair game. Frearson and Smith decided to try it out on Australians from Oxford and Cambridge who were playing an Aussie Rules football match for a combined universities eighteen against a scratch team of Australian sailors from a visiting ship. Bob Hawke and his fiancée, Hazel, were among the Australians who travelled from Oxford to London for the game. It was played in the snow on a very cold day and the Navy, who were in better condition, won. Feeling slightly disconsolate, sore, and in need of warmth and good cheer, members of the universities side went to a tavern recommended by Frearson. Hawke had a reputation as a big drinker. He had set a new sconce record at Oxford by drinking two and a half pints of beer in twelve seconds, for which he got his name in the Guinness Book of Records. Frearson told him about the marvellous Colne Spring Ale and how he and his friends had got plastered on it. He added, “Three of those and you’ll be full.” Hazel did not drink but Hawke and his other companions could not resist the challenge, and in Benskins they met their match. Frearson vaguely remembers the whole scene disintegrating: he recalls a toothless old woman playing the honky-tonk in the pub – not much else. Near closing time Hawke, Frearson, Smith and two girls from Perth weaved out of the pub and piled into Hawke’s rattletrap van. With the still sober Hazel at the wheel they drove off into the whirling night, singing uproariously a snatch from a half-remembered song.

“Half a crown” is two shillings and six pence, which means those were half-pint bottles of CSA Hawke and his university pals were drinking, since in 1953, about the same time, “nip” (six and two thirds fluid ounce) bottles of CSA were one shilling and eightpence. CSA, according to Ron Pattinson’s notes, had an alcohol by volume in 1953 of 10.95 per cent. Three half-pint bottles would be the equivalent of not quite four and a half pints of “ordinary” bitter, or around a bottle of wine. Drink that quickly enough, without food (and what pub served food in early 1950s Britain?), and I’m sure you would feel “full”. I doubt, as perhaps you do, that Hawke and his pals stuck to just three half-pints, either, though a writer in 1949 said that Benskin’s licensees were not supposed to serve more than four bottles of Colne Spring Ale to any one customer – “and four bottles is quite enough”.

That abv, from an original gravity of 1090.7, was achieved through a remarkable attenuation: just under 91 per cent. A couple of other brewers were achieving similar attenuations at the time with big, bad brews, but most high-gravity beers in Britain at the time were seeing attenuations in the 60 to 79 per cent range. How were Benskin’s achieving this? By deliberately adding a Brettanomyces culture to the beer after its initial brewing, and then storing it in casks for months in cellars that sat below the maltings at the brewery in Watford. There the slow-acting Brett yeast found an environment where it could flourish, already quite high in alcohol, which cut down on competition from less alcohol-tolerant organisms, and with the oxygen that, unlike “normal” brewer’s yeast, Saccharomyces cerevisiae, it preferred to maximise its own alcohol production, it could work away, increasing the beer’s strength while adding a unique cocktail of esters and acids.

That wasn’t a trick the brewers knew when Alfred Barnard sampled Colne Spring Ale in 1890: they certainly kept the beer for months to mature, but they never actually deliberately added Brettanomyces. It was, instead, simply in the air, or, more accurately, in the wooden brewing vessels, tubs, tuns, backs and casks they used, just as it was in every other brewery in Britain. However, while brewers after the researches of Louis Pasteur in France and Emil Christian Hansen in Denmark knew about Saccharomyces cerevisiae, they remained unaware of the existence of Brettanomyces. They only knew that while the “pure yeast culture” ideas that Hansen pioneered at the Carlsberg brewery in Copenhagen might work with continental beers, British ales and stouts failed to achieve a satisfactory secondary fermentation, and failed to arrive at the full range of flavours desired by connoisseurs, if they pitched with a “pure” yeast selected from just one strain.

It took another Dane, Niels Hjelte Claussen, a younger colleague of Hansen’s at Carlsberg in Copenhagen, to discover what was going on. In or shortly before 1903, Claussen isolated a previously unknown type of yeast from a sample of English “stock” (that is, well-aged) beer that was, he discovered after experimenting with it, the source of those “mature” flavours associated with aged English ales, beers, porters and stouts. In honour of its origins, Claussen named this newly found yeast “Brettanomyces”, from the Greek for “British”, “Βρεττανοί”, and “fungus”, “μύκης”

Soon after, Claussen spoke to a meeting of English brewers at Brewers’ Hall in the City of London in April 1904 about his experiments with Brettanomyces:

“I have fermented with English single cell top yeast a Danish stout wort prepared by decoction mashing, and, after addition of Brettanomyces and 2 or 3 weeks storage, I bottled the beer, which was then left to stand for a fortnight at a temperature of 77 F. According to the verdict of several connoisseurs, the product thus obtained was in no way inferior to the best sorts of London stout, whilst parallel bottles which did not contain Brettanomyces entirely lacked the English character.”

Brettanomyces, Claussen (who only died in 1955) told his audience at Brewers’ Hall

“produces a slow fermentation in wort, or in beer fermented with ordinary brewer’s yeast. The carbonic acid developed by its action is retained very firmly, and when set free by agitation, forms a copious and lasting foam. In the course of the fermentation, rather a considerable amount of acid is formed, accompanied by ethereal substances, the taste and flavour of which cannot fail to attract the attention of any connoisseur by their striking resemblance to the flavour of stored English beers.”

In the average English brewery, he said, Brettanomyces

“exists as a general infection … I suppose it invariably forms a minor constituent of English pitching yeast and it may probably be found in all such places in the pipes utensils and vessels of the breweries where such infections may creep in and get fixed.”

It was the lack of Brett in pure-yeast cultures that meant pure-yeast brewing did not produce the required taste in English beers. The action of Brettanomyces, Claussen said, was

“absolutely necessary to bring English stock beers into proper cask and bottle condition, and to impart to them that peculiar and remarkably fine favour which, in a great measure, determines their value.”

It was, he said,

“very easy to furnish a direct and striking evidence of its being so. If we add to pasteurised beer a slight portion of a Brettanomyces culture in wort, say a few drops to a bottle of the beer, and if we then leave the beer to stand in well corked bottles at a temperature of 75-85F during 10-14 days, a slight deposit will be observable, and at the same time the beer will assume an unmistakable English character, both in regard to its content of carbonic acid gas and to its taste and flavour.”

Trying the same trick on Continental bottom-fermented beers, Claussen said, and even poorly attenuated Continental top-fermented beers, led to a beer with “a somewhat impure taste”. It was probably unnecessary, he said, to make sure English “running” beers, “which do not undergo any secondary fermentation”, came into contact with Brett. But

“with the various sorts of stock beers, the case is quite different. In the case of these beers, the action of Brettanomyces is a necessary condition for the production of a beverage possessing the properties wished for, and it is therefore necessary, after the yeast has done its work and has been separated off, to add a pure culture of Brettanomyces.”

This could be as little as a pint of 1055 OG wort in which a pure culture of Brett had been grown for a week to every five barrels of beer, Claussen said, added when the primary fermentation was over. The addition of Brettanomyces could make a considerable difference to the strength of the final beer: “Some varieties produced a considerable quantity of alcohol, eg 4 or 5 per cent, but it took a long time. It was a very slow fermentation,” he told the meeting. However, any British beer stored for five or six weeks or longer would benefit from the addition of a little pure Brett culture, Claussen said.

Alas, Claussen’s revelations came just as the “peculiar and remarkably fine flavour” of stock ales and stouts was going out of fashion. As one of the audience at the meeting in Brewers’ Hall, the brewing chemist Dr Edmund Moritz, told the speaker, the types of beers in which Brettanomyces evidently played such an important part were becoming “every day less important, because the tendency of modern brewing was against the production of stock beer, and the substitution of what possibly Mr Claussen might call a running beer, viz a beer kept anywhere between four and 12 days before it was sent out of the brewer’s cellar.”

Unsurprisingly, Brettanomyces later turned up in maturing Guinness stout, and researchers also found different sorts of Brettanomyces yeasts in Belgian lambic beers. However, Brett character became, with the exception of beer such as Colne Spring Ale, something British brewers tried to eliminate from their breweries. After the First World War, more and more beers in Britain were low in gravity, and Brett flavours and aromas do not seem to go with low gravity beers.

Colne Spring Ale continued, however, impregnated with Brett (presumably after Benskin’s brewers took heed of Claussen’s suggestion to add the yeast deliberately rather than rely on any infections in the brewery’s vats and casks), still naturally conditioned in the bottle, and depending on which source you believe, matured in the brewery’s cellars for “at least a year” or as long as seven years. Wartime restrictions finally brought its brewing to a halt in 1944, but it was revived again in 1951. However, the post-Second World War version appears to have been pasteurised, rather than naturally conditioned. Even so, Andrew Campbell said of it in 1956 that it was ” dark [37 on the Lovibond scale, as dark as Benskin’s Nut Brown Ale], mellow, and pours like wine, very slightly carbonated. It is rich and luscious in flavour, in no way edulcorated [sweetened] … beer that should be treated with the very greatest respect.” It looks, judging by the attenuation, and that “not sweet” comment by Campbell, to have still been brewed with an addition of Brett.

Colne Spring Ale survived Benskin’s takeover by Ind Coope in 1957, and only ceased production in February 1970, two years before the Watford brewery itself closed. The name was revived briefly by Allied Breweries in the mid-1980s, albeit at a vastly reduced strength. But my writing about CSA in Amber Gold & Black, my book from 2010 on the history of British beerstyles, from mild to barley wine, apparently inspired Ed Wray to recreate it, and he was nice enough to send me a bottle.

How was it? Very good: liquorice and toffee apples, the lightest hint of ginger, a touch of – don’t laugh – cooked egg yolk, the faint sweaty, gym floorboards hint of Brett. The underlying sweetness, was perhaps TOO sweet for complete historical accuracy: maybe (what do I know? I’m not a brewer, despite my pretentions) the Brett should have been given more time. But it would definitely be on my shopping list.

I had a genuine nip-sized bottle of Watford-brewed Colne Spring Ale from the Ind Coope era to compare with Ed’s homage, but alas the past 40-odd years had been unkind, despite it being sealing with a cork-lined crown top. It had a much fuller, oilier mouthfeel, with hints of bread pudding and baked raisins, but the overwhelming taste was the “chocolate liqueur” flavour I’ve had before in aged bottled beers that have turned up their toes. There was the ghost of past character apparent, but ultimately age had done for this beer, and it was a sinkpour – a needed reminder that not all very old beers are going to be any good.

Conclusions? I wished I had experimented with adding small amounts of Femme Fatale to other beers: it would be extremely interesting to see how just a touch of Brett reacted with, eg, an Imperial Stout, an American IPA, a brown ale. The current American obsession with all-Brett beers is not going to get very far, certainly in Britain: it really is the exact beery equivalent of the how-hot-can-you-make-your-curry loonies. But Brett is an extremely useful spanner in the creative brewer’s toolbox: as a fan of historical reproductions I hope to see a few more new beers with a touch of Brett appearing on the market, using the techniques outlined by Claussen 108 years ago, and I congratulate Ed Wray for an excellent first effort.