The Viking left this morning, having sated his appetite for destruction on my flat and property. i’ve seen him about once a year since we graduated in 2001 – every visit has been marked by chaos and destruction and insanity. Just some of the things he has done: in 2004 he destroyed my father’s car, which led to my expulsion from the family bosom; in 2007 he summoned a schizophrenic girl to break into the house at 0800.

This time he merely destroyed my fob watch and the light in the bathroom, and awoke a pagan madness in the Germans on New Year so the streets looked like something from Mad Max 2 (street fires, rockets firing horizontally at eye level, packs of crazed Germans running through the streets screaming, gnawing on human bones etc.), also he made a kind of Viking stew and did an inexplicable robotic kind of Viking dance.

It has been an interesting few days. The Viking is a severe and scowling Christian Chemist, or at least he thinks he is – really, he is a pagan deity of some sort, an embodiment of chaos, disorder, repressed homosexuality, and destruction. He is also habitually larcenous – he takes “look at this” to mean “I am giving you this forever – wait until my back is turned and then put it in your bag.” After each visit i find things have disappeared – books, CDs, and DVDs usually – but he compensates by leaving unwanted items behind, e.g. chemistry textbooks, odd socks, sweet wrappers, children’s comics, water pistols, CS Lewis books, diodes, electric cable, broken test tubes, beard clippings, obliterated hats, strangled children, and assorted unidentifiable and radioactive matter. Also he likes to destroy papers and books by nervously and unconsciously ripping them up and making them into origami figures of, for example, his mother, God, John Calvin, and so on, usually while talking about demons.

It is also a Viking tradition to attempt to have us both arrested or murdered. On previous visits he has: stared maniacally at drug dealers in petrol stations at two in the morning, and then leaned over to inspect their purchases and count their change; said things like “that is one thing I miss about Germany – cheerful black people” in Leeds, so everyone can hear; sung Leonard Cohen songs in public; drawn offensive caricatures of people in bars, and then handed them over to the subjects, proudly.

This year he fulfilled this proud Viking tradition as follows:

1. As we were trudging through the snow he suddenly bounded jerkily across the road to a military-looking building, guarded by CCTV and menacing signs. As i stood anxiously by he leapt into the bushes under the windows, explaining: “I require these berries!” He emerged with a withered, inedible berry, exclaiming proudly: “These can be made into jam!”

“But Jonah,” i said, to no avail, “we have jam at home.”

However, for the Viking, illegal foraging and makeshift chemistry-in-the-kitchen is an end in itself. The jam is merely the occasion. Throughout his visit he insisted on foraging for vegetable matter for a jam which, mercifully, never appeared. However, i am in no doubt that he will have left these berries all over the flat – hidden, of course – and they will come to light when they decompose or attract rodents.

2. In the bank, as i was queuing to find out why i couldn’t take any money out of my account, he peered ostentatiously over to spy on a woman ahead, commenting loudly, “Hmm, interesting – she is taking out American dollars.”

“Please don’t spy on people’s financial transactions,” i said wearily.

“I am not. I am merely making a scientific observation. Hmm. Interesting. Her bank account number is -”

“Jonah. Please. Making scientific observations about other people’s bank accounts, so they can hear, is generally frowned upon these days.”

“I do not see why anyone could object. I am merely expressing my scientific curiosity.”

3. While i was checking the flat postbox by the front door, he was busily trying to pry open another box, hammering at it with his fist and peering through the letter flap. When i expressed a strong disapproval, he was, as usual, perplexed, and said he had just been “hitting the wall” out of boredom.

So, somehow neither of us were arrested or deported or murdered. He destroyed the bathroom light, which of course came back to life the day after he left; he destroyed my fob watch; he is the Viking – and he will live forever.