Professor Jacob Marbles presents a striking image as he answers his front door, although not necessarily for the right reasons. He wears a tattered, camel-coloured dressing gown over a cable-knit sweater, decorated with tea stains and long forgotten breakfasts. Strands of straggly salt and pepper hair sweep majestically over the dome of his thinning pate, although not in any deliberate way. More in the manner of someone caught out in a storm. His attire also appears to be fairly liberally coated in cat hairs, a fact that becomes all the more curious when I later discover that he hasn't got a cat.
"We don't want any," he snaps, with a venom that is sure to leave even the most tenacious of door-to-door merchants in no doubt that the pickings at this address will be meagre. The door starts to close and I try to rally sufficiently to effect an explanation of my presence, but I appear to be conversationally winded.
Help arrives at the last minute in the form of the Professor's nurse who gently releases her charge's iron grip on the door and explains to the venerable old geezer that I am the man who has been sent to interview him. Despite this, it is still with some degree of caution that the Professor allows me to enter.
Such awkwardness is only to be expected, as anyone with even the most fragile familiarity with the Professor's history will confirm. I had never met him before but I have spoken to those who have and clearly they still bear the scars. Professor Marbles has never been known to be particularly active socially and he is even more reserved in professional circles. Yet despite his habit of keeping himself to himself, he has a reputation for offending more people, and being thrown out of more places, than anyone. It seems that even the briefest contact with him is enough to start a fracas, which perhaps explains why his nurse is so keen to keep him locked up at home.
His legendary hospitality is once more in evidence as we take our seats in the front room and the nurse offers me a cup of tea.
"Help yourself!" snarls the Professor. "Finish off the milk while you're at it. I suppose you want a biscuit?"
I politely decline this generous offer but the Professor won't hear of it and insists that I have a custard cream. In fact, he's so anxious that I should partake of his generosity that he picks up the aforementioned biscuit and hurls it in my direction. I duck, feel the biscuit whistle past my ear and hear the chink of china as it ricochets from the dresser behind me.
The Professor's magnanimity knows no bounds and a further three custard creams, a couple of jammie dodgers and a chocolate hob nob are propelled in my direction before his nurse is able to disarm him. And not before time too, as I fear that if the livid trail of crumbs across my cheek was anything to go by, the Professor was just getting his aim in.
For a man of genius, this kind of eccentric behaviour is easily overlooked. According to reports, however, Professor Marbles' behaviour is widely frowned upon by his colleagues, and those colleagues entertain similar misgivings on the subject of his genius. This is odd, because if said colleagues have any expectations of enjoying a long and prosperous career, then it will be Professor Marbles that they need to thank.
So why would their future prospects ever be in doubt?
"Because of the impending discovery of a grand unified theory, you cretin," says Professor Marbles as he leans forward and gobs in my tea. "The theory of everything - profound enough to put an end to our search for knowledge and simple enough to print on a T-shirt. Now, I expect you're about to ask me something incredibly stupid. You are, aren't you? I can see it welling up in you."
I hesitate. The nurse has left the room and suddenly I feel very alone and vulnerable. There is nothing for it but to press on, so I ask why this discovery would have such an impact. Even though he has apparently anticipated this question, Professor Marbles nevertheless feels it necessary to demonstrate his displeasure by hurling a coal scuttle at my head. It misses and clangs into the wall behind.
"Ask yourself this," he hisses as the echoes fade away. "Once we understand everything there is to know about the universe - once we can finally fill in those missing pieces in the jigsaw, comprehend the intricate workings of reality and describe the delicate interplay of forces and properties that underpin the very nature of existence - once we know all that, what is left?"
I patiently wait for him to tell me. He glares at me, his eyes bloodshot and bulging, the tendons stretched taut in his neck. I feel sure the question is meant to be rhetorical but he seems to be expecting me to answer. I fear a trap, but my nerve gives out first.
"Well, I suppose the nature of consciousness - "
"Pah!" he cries venomously. "What would you know of consciousness; you're barely awake as it is? No, there would be nothing left. Nothing left to discover. Not proper science stuff anyway. Oh yes, you're always going to get people fiddling about with new types of washing power and developing different flavoured dog food, but the big stuff - kaput!"
"Kaput!" the Professor emphasises with a rude gesture. "Which means all those scientists will be out of work. Think of that, hmm? No? You can't, because it's unthinkable. Those people haven't got a clue what it's like in the real world. They stepped straight out of university and straight into a lab coat. It would be chaos."
"Which is where your Unknowable Theory comes in?" I ask cautiously and then flinch. In the short time I have known Professor Marbles, this reaction has become autonomous. However, much to my surprise he doesn't take it as a cue to fling something sharp at me.
"That's right, lad," he says gently. "You've got it." He even gives me a playful wink. It is all deeply, deeply disturbing and I find myself on my guard more than ever as he goes on to outline the thinking behind his theory.
"What we needed was an idea so radical, so extraordinary and so impossibly impenetrable that no one will ever be able to get to grips with it. Unknowable Theory is precisely that. If you think you've understood it, then you haven't. The only thing that we can say about it with any degree of confidence is that it is impossible to know anything about it... also, it has something to do with zebras."
At a recent lecture in Vienna the Professor spent nine hours explaining his theory to eight hundred of the planet's most accomplished - and expensive - scientists. He showed over four thousand slides and diagrams, made use of hardware specially loaned for the occasion by the Jet Propulsion Laboratory and drew upon reams of the very latest cosmological research. Nobody could follow a word of it. He received a standing ovation and as the assembled boffins filed out of the auditorium, clutching their packets of complimentary chocolate digestives and massaging their aching buttocks, it was as if a great burden had been lifted from their shoulders. Here at last was a field of research that would occupy scientists for centuries and happily keep everyone in clover for life.
But can we really be confident that we will never crack Professor Marbles' impenetrable conundrum? Is there not a danger that somewhere, someday, some smart aleck will go and ruin it for everyone by finally figuring it out? When I put this question to the Professor he responds with a string of abuse and I quickly dodge the tea tray that comes spinning through the air and smashes into the ornaments on the dresser. I feel that I'm back on comfortably familiar territory.
"My theory isn't just some half-baked notion dreamt up by a loser like Einstein or Newton," he drools and splutters as he fidgets about excitedly in his chair. Unknowable Theory is so completely radical that we need a whole new language to describe it. I am currently devising such a language but I need six more consonants."
Even so, I reason, is it not possible that someone might conceivably... I get no further than this as Professor Marbles demonstrates that he has finally had enough of this line of questioning. He calls for his nurse who returns promptly with a loaded shotgun. Persuaded to leave my final query unanswered, I take it upon myself to show myself out and make it to the door just in time to hear a loud explosion and perceive a vase exploding into a shower of fragments somewhere close by.
I sprint down the street and around the corner before stopping to regain my breath. Whatever the merits of Professor Marbles' theory, I reflect, if it serves to keep him and his kind occupied and away from normal society, then that can't be a bad thing. I think we'll all feel a lot safer if it continues to do so for many years to come.