At one point we gather around the rim of an extinct volcano vent, listening to the guide. In the winter of 1903, he says, the local postman fell down the vent and couldn't climb out.
Our guide's account of the postman's adventure is long, implausible and involves the first telephone call ever made in north Iceland.
But the conclusion is a happy one. To celebrate, the guide produces a bottle of homemade moonshine, then a tower of plastic shot glasses, and we drink first the postman's health, then the telephone company's.
'Please be careful,' says the deputy guide, Halltor, a pokerfaced chap who had hitherto not spoken a word. 'We will drink a lot today. Pace yourselves.' In the afternoon we visit an old herring processing factory at a place called Ektafiskur.
Our host, Elvar Reykjalin, is a fifth generation cod fisherman with a face as unexpressive as a lump of volcanic debris.
This man unsmilingly welcomes us to his gutting station with a bottle of homemade alcohol. Once more we feel the liquid potency sliding down our oesophaguses like hot magma. Halltor catches my eye and waggles a stern finger.
Now blinking back tears, we stand around a steel table and watch in respectful silence while Mr Reykjalin slits open a magnificent 15lb cod and guts it with skill. The liver is as big as a pig's. Three sweeps of the blade and it's on the table.
Three more incisions and the stomach is dangling between his scarred thumb and forefinger.
Pressing out its contents to leave an empty, prophylactic-shaped sac, he asks us, with maybe a hint of lasciviousness, whether we have ever wondered why there are so few people in Iceland.
Before we can answer, a flick of his wrist detaches an eyeball. This he pops into his mouth, like a gobstopper. Then runs around the table and menaces the most obviously squeamish member of our party with it.
He makes us each eat a piece of rotten shark flesh, which is a famous Icelandic delicacy. At least that's what he tells us. Those who swallow, rather than gag or spit, are awarded a certificate and another shot of moonshine. I eat two lumps and receive a double shot.
Finally Mr Reykjalin reveals the corpse of a weird primeval sea monster lying rotting in a tank. It's a 500-year-old Greenland shark.
In its stomach they found an entire seal. 'Our lunch,' he says. 'The shark, not the seal. Or maybe it is the seal. I'll ask.' Murmurs of dismay from our party. 'I am joking,' he says, expressionless as before.
Then we go to the Kaldi brewery to bathe naked in wooden tubs of warm beer. Beside each tub is a frosty tap and clean glass. 'Drink as much beer as you like,' says the hostess. 'But not too much,' adds Halltor in a private aside to me.
After that we visit the beermaking plant. The head brewer is sober of speech and manner. He dispenses his samples unstintingly by the half pint.
There are nine different kinds of beer, the strengths ranging from five to nine per cent. The Kaldi Chocolate Christmas Porter is excellent. Halltor's glass, I notice, is always first and foremost for a top-up. We drive on to another brewery, this one called Segull 67, for another tasting. By now I have cast off all pretence of curiosity in the beer-making process and am seeing double.
As our glasses jostle at the nozzle, I catch Halltor's eye. Up came the admonitory finger, but tipsily this time, and his poker face creases into laughter. Finally I got the joke. 'Pure spirit' indeed. 'Pace yourself'— ha!
If I had to characterise those north Icelanders in a phrase, it would be 'wonderful deadpan comedians'.
Travel Facts
Super Break's (superbreak.com, 01904 717 362) Incredible Iceland package starts in January 2018: operating from UK airports. From £779 (NZ$1472) pp, based on four nights' B&B at Hotel Kea by Keahotels, Lake Myvatn tour and Northern Lights tour and flights from Stansted on February 19.
