As they walked the older man was doing all the talking. He was pointing at items of interest along the way, despite the fact that it was too dark to see any of them. The younger man was saying «Ah yes,» and «Really? How interesting…» and «Well, well, well,» and «Good heavens.» His head bobbed seriously.

They entered, not through the main entrance to the hall, but through a small doorway on the east side of the court. This led to the Senior Combination Room and a dark-panelled anteroom where the Fellows of the college assembled to slap their hands and make «brrrrrr» noises before making their way through their own entrance to the High Table.

They were late and shook off their coats hurriedly. This was complicated for the older man by the necessity first of taking off his professorial gown, and then of putting it back on again once his coat was off, then of stuffing his hat in his coat pocket, then of wondering where he'd put his scarf, and then of realising that he hadn't brought it, then of fishing in his coat pocket for his handkerchief, then of fishing in his other coat pocket for his spectacles, and finally of finding them quite unexpectedly wrapped in his scarf, which it turned out he had brought after all but hadn't been wearing despite the damp and bitter wind blowing in like a witch's breath from across the fens.

He bustled the younger man into the hall ahead of him and they took the last two vacant seats at the High Table, braving a flurry of frowns and raised eyebrows for interrupting the Latin grace to do so.

Hall was full tonight. It was always more popular with the undergraduates in the colder months. More unusually, the hall was candlelit, as it was now only on very few special occasions. Two long, crowded tables stretched off into the glimmering darkness. By candlelight, people's faces were more alive, the hushed sounds of their voices, the clink of cutlery and glasses, seemed more exciting, and in the dark recesses of the great hall, all the centuries for which it had existed seemed present at once. High Table itself formed a crosspiece at the top, and was raised about a foot above the rest. Since it was a guest night, the table was set on both sides to accommodate the extra numbers, and many diners therefore sat with their backs to the rest of the hall.

«So, young MacDuff,» said the Professor once he was seated and flapping his napkin open, «pleasure to see you again, my dear fellow.

Glad you could come. No idea what all this is about,» he added, peering round the hall in consternation. «All the candles and silver and business. Generally means a special dinner in honour of someone or something no one can remember anything about except that it means better food for a night.»

He paused and thought for a moment, and then said, «It seems odd, don't you think, that the quality of the food should vary inversely with the brightness of the lighting. Makes you wonder what culinary heights the kitchen staff could rise to if you confined them to perpetual darkness. Could be worth a try, I think. Got some good vaults in the college that could be turned over to the purpose. I think I showed you round them once, hmmm? Nice brickwork.»

All this came as something of a relief to his guest. It was the first indication his host had given that he had the faintest recollection who he was. Professor Urban Chronotis, the Regius Professor of Chronology, or «Reg» as he insisted on being called had a memory that he himself had once compared to the Queen Alexandra Birdwing Butterfly, in that it was colourful, flitted prettily hither and thither, and was now, alas, almost completely extinct.

When he had telephoned with the invitation a few days previously, he had seemed extremely keen to see his former pupil, and yet when Richard had arrived this evening, a little on the late side, admittedly, the Professor had thrown open the door apparently in anger, had started in surprise on seeing Richard, demanded to know if he was having emotional problems, reacted in annoyance to being reminded gently that it was now ten years since he had been Richard's college tutor, and finally agreed that Richard had indeed come for dinner, whereupon he, the Professor, had started talking rapidly and at length about the history of the college architecture, a sure sign that his mind was elsewhere entirely.

«Reg» had never actually taught Richard, he had only been his college tutor, which meant in short that he had had charge of his general welfare, told him when the exams were and not to take drugs, and so on. Indeed, it was not entirely clear if Reg had ever taught anybody at all and what, if anything, he would have taught them. His professorship was an obscure one, to say the least, and since he dispensed with his lecturing duties by the simple and time-honoured technique of presenting all his potential students with an exhaustive list of books that he knew for a fact had been out of print for thirty years, then flying into a tantrum if they failed to find them, no one had ever discovered the precise nature of his academic discipline. He had, of course, long ago taken the precaution of removing the only extant copies of the books on his reading list from the university and college libraries, as a result of which he had plenty of time to, well, to do whatever it was he did.

Since Richard had always managed to get on reasonably well with the old fruitcake, he had one day plucked up courage to ask him what, exactly, the Regius Professorship of Chronology was. It had been one of those light summery days when the world seems about to burst with pleasure at simply being itself, and Reg had been in an uncharacteristically forthcoming mood as they had walked over the bridge where the River Cam divided the older parts of the college from the newer.

«Sinecure, my dear fellow, an absolute sinecure,» he had beamed. «A small amount of money for a very small, or shall we say non-existent, amount of work. That puts me permanently just ahead of the game, which is a comfortable if frugal place to spend your life. I recommend it.»

He leaned over the edge of the bridge and started to point out a particular brick that he found interesting. «But what sort of study is it supposed to be?» Richard had pursued. «Is it history? Physics? Philosophy? What?»

«Well,» said Reg, slowly, «since you're interested, the chair was originally instituted by King George III, who, as you know, entertained a number of amusing notions, including the belief that one of the trees in Windsor Great Park was in fact Frederick the Great. It was his own appointment, hence „Regius“. His own idea as well, which is somewhat more unusual.»

Sunlight played along the River Cam. People in punts happily shouted at each other to fuck off. Thin natural scientists who had spent months locked away in their rooms growing white and fishlike, emerged blinking into the light. Couples walking along the bank got so excited about the general wonderfulness of it all that they had to pop inside for an hour.

«The poor beleaguered fellow,» Reg continued, «George III, I mean, was, as you may know, obsessed with time. Filled the palace with clocks. Wound them incessantly. Sometimes would get up in the middle of the night and prowl round the palace in his nightshirt winding clocks.

He was very concerned that time continued to go forward, you see. So many terrible things had occurred in his life that he was terrified that any of them might happen again if time were ever allowed to slip backwards even for a moment. A very understandable fear, especially if you're barking mad, as I'm afraid to say, with the very greatest sympathy for the poor fellow, he undoubtedly was. He appointed me, or rather I should say, my office, this professorship, you understand, the post that I am now privileged to hold to — where was I? Oh yes. He instituted this, er, Chair of Chronology to see if there was any particular reason why one thing happened after another and if there was any way of stopping it. Since the answers to the three questions were, I knew immediately, yes, no, and maybe, I realised I could then take the rest of my career off.»