I was reminded of the episode this week when I tasted the brew derived from those samples. The beer was the colour of lemon marmalade, and had yeasty aromas and flavours reminiscent of apples, toffee and spices. They were the flavours of the past, reaching far beyond the beer's production last month at a mere 200-year-old brewery in Wisbech, Cambridgeshire.
Among the living traditions of beer-making in Europe today, the oldest - perhaps a missing link - are those of home brewing in rural communities in Finland, Sweden and Norway. These existed long before their temperance-minded governments rendered commercial beer expensive and hard to find.
Early beers were fermented by airborne wild yeasts. Norse legend says that Odin, disguised as an eagle, spilled the secret of beer from the sky. The Norwegian brewers learnt that, if they kept the stick they had stirred their previous brew with, it would help to start the next fermentation. Coated with sticky residue, the 'magic sticks' harboured millions of living yeast cells. Later called 'yeast logs', some have been kept as family heirlooms.
Today, in the rural valleys of the mountainous west, almost every farmer keeps a supply of liquid yeast for home-brewing, and all say that this precious resource has been in the family 'for as long as we can remember, probably from Viking times'. To explore this culture, I took the train from Bergen to the mountain town of Voss, where most visitors ski or fish for salmon.
This was the train that had until recently been driven by a local man named Arthur Applethun. A year or two after his retirement, Mr Applethun learned that he was terminally ill. He called his daughters, Gerd and Anne-Magrethe, and told them his last wish, which they translated for me as follows: 'I would like to think that our family will always have beer to give our guests, and that it will be a brew we ourselves have made. I don't know whether you girls can brew, but I would like you to try.'
'Our first malt was our father's,' Gerd said. 'Our yeast is, and will always be, our father's. It is his yeast, and it is still alive. When it gives us beer, it is like being with our father again. It means home and family and sociability.'
From Voss it is at least 10 miles (the last couple on rocky tracks through forest) to the spruce cabin where the sisters brew. In the middle of the cabin is an open fire, above which their cauldron-like brew-kettle is suspended from a metal crossbar. When they were not brewing, sides of meat could be hung to smoke. Or the fire could be partially covered with a metal hotplate on which crispbread could be baked.
The sisters' beer tastes smoky, with a touch of treacle toffee, but it is also intensely dry and fruity, with tinges of juniper. Farmhouse brewers in Scandinavia often use juniper berries as a flavour and preservative (in this role, they probably pre-date hops), and filter the beer through a bed of the twigs.
One morning, I climbed a hillside with another farmhouse brewer, Svein Rivenes. He showed me the stream where he had tied a sack of barley so that it would germinate - a primitive form of malting. On the hillside we cut juniper bushes to use in his next brew.
As soon as a fire was set under the kettle and the smoke issued like a signal from the chimney, neighbours started arriving to help. Each brought samples of beer, so that we could quench our thirsts in the heat of the brewhouse. 'This is our equivalent of a pub,' said Svein.
The scale of activity rendered the term 'home-brewing' insufficient: Svein had 700 litres in his kettle, and I would call that 'community brewing'. By law, farmers can brew as much as they like, so long as they use barley they have grown themselves. I heard stories of illicit truckloads of barley-malt arriving in the middle of the night. 'Don't the police stop it?' I asked a community brewer in another town. 'Not here,' he replied. 'I'm the chief constable.'
A few days later, we drank Svein's beer at the Sheep's Head Festival. Once the year's lambs have been slaughtered, the people of the valleys around Voss look forward to feasts of smoked sheep's head in early October. The sisters were there. 'Home-brew and sheep's head]' one of them exclaimed to me. 'Without the home brew, you may as well leave the head on the sheep.'
The head seemed to be smiling at me in profile on the plate. With some difficulty, I obeyed the instruction to begin with the soft fat behind the eye. It tasted like fatty salt beef. They assured me that it was a great delicacy. To bless our dinner, a man in a Viking helmet recited some lines from a saga.
Afterwards, I asked Svein if I could bring a sample of his 'Viking' yeast back to Britain. I wanted to show it to Keith Thomas, a brewing scientist at the University of Sunderland. Mr Thomas has taken a particular interest in yeasts, and once made a porter with a culture found in bottles from a shipwreck at the bottom of the Channel. He argues that while today's barley malts and hops can be more or less matched to recipes from the past, the yeast, being a living organism, is its most elusive element and easily lost for ever. The malt and hops make body and character, but yeast is the soul.
Mr Thomas said that he would experiment with the yeast at a small commercial brewery, to make a product called Original Viking Ale. He started with a five-barrel batch, then moved to a larger brewery where he could make 20. Now, he has produced a 50-barrel batch at Elgood's, the Wisbech brewery better known for its Cambridge Bitter.
The malt used in the new product comes from East Anglia, and hops from Kent, Hereford and Worcester are being preferred for the moment to juniper. The Norwegian farmer's yeast, however, still imparts decidedly 'Viking' tastes, even at 4 per cent alcohol (compared to twice that level in Voss).
Despite eating the sheep's head to prove my worthiness, I have been offered no royalty on the brew. But then I was only the courier - the yeast came from Odin.
Original Viking Ale is available from specialist beer shops and some licensed wholefood stores. It is distributed by Vinceremos Wines and Spirits of Leeds (0532 431691).
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