We had to write a story about guilt. That was such a broad concept that initially I found it hard to come up with anything. However I'd just been reading a biography of the writer Harlan Ellison and an incident from his life suggested an idea to me.

The sign above the door says: BANCROFT AND SON, BOOKSELLERS. It's not telling the whole truth. SON was my father and BANCROFT himself was my granddad. I don't have any children which is probably just as well because running a bookshop has got a lot more difficult over the years since I inherited the business from my dad, and I wouldn't want to wish today's retail problems on anyone else.  In my father's day it was easy. The publishers' reps came round every month with a list of new titles, we ordered the stock we felt we could easily sell, the books were delivered and then we sold them. Simple.

It's very different now.  Most people buy their books on the internet these days and I've had to completely change the way I do business. My father wouldn't recognise the place. I specialise in books from small press publishers – very expensive limited editions, beautifully bound and often presented in slipcases. You can buy those on the internet as well, of course, but the people who tend to seek out and collect these kinds of books much prefer to come to a real shop where they can examine the books before they buy them. They like to pick the books up, flip through the pages, smell the ink and feel the weight of the book in their hands. For these people, book buying is a very tactile experience. The internet can't give you that to you. Not yet, anyway.

I like to organise autograph sessions as well. They are always good for business. I buy a lot of extra copies of as many different books by the author as I can find. The author sits in the shop, people buy the books and then get them personally signed. If the author is popular enough, I can often have long queues of people waiting patiently to get their books autographed and by the end of the day I've usually sold more than enough to keep the shop ticking over for another few weeks.

Not so very long ago I arranged an autograph session with Barry Anderson. You might not have heard of him. He's a bit of an odd character in this day and age of huge and heavy blockbuster novels that you really don't want to drop on your big toe. He only writes short stories. Every couple of years or so he publishes a slim collection of his elegantly twisted tales. Strangely, they sell very well and he makes quite a nice living from them, though I don't know how he manages it. Nobody else seems to be able to do that.

The other interesting thing about Barry Anderson is that he's an example of local boy makes good. He was born here in the town and I often used to see him in the bookshop when he was just a child. He spent many hours in here, browsing the shelves and reading the books, always being very careful not to crease the spines. And, of course, he never, ever turned down the corner of a page to mark his place. When Barry put a book back on the shelf, nobody would ever know that it had been read diligently from cover to cover. If he found a book that he particularly liked, he would positively glow with happiness. I enjoyed seeing that happen.

Barry was also a very skilful shoplifter who liked to take his really special books home with him to keep. My father was always puzzled when he reconciled our stock records with the till receipts and found missing books that he simply couldn't account for. I knew that Barry was taking them, but I never told my father. I felt that someone who enjoyed books as much as Barry did deserved to have them to keep, even though he couldn't afford to buy them. My father, curmudgeon that he was, would never have agreed with me, so I kept quiet. Perhaps that's another reason why I find it so hard to make a living running a bookshop. I'm not the cold type of businessman that my father was.

To prepare for the autograph session, I set up a nice solid table with a comfortable chair at just the right height for Barry to sit in and sign books without any strain. I put piles of his story collections at strategic locations throughout the shop. About an hour after I opened the shop, Barry arrived. I recognised him immediately.

"Hello," I said, shaking his hand. "Welcome back to Bancroft and Son. It's good to see you again."

"Hello," said Barry. He looked uncomfortable and a little nervous.

"I've got everything ready for you," I said. "Hopefully we'll get a good crowd in."

"Err, yes," said Barry diffidently. And then, not meeting my gaze, he asked "Did you notice anything unusual when you unpacked the books?"

"No," I said. "Should I have?"

"There wasn't an invoice included with them," said Barry, looking me in the eyes for the first time.

"That's right," I said. "I assumed it was just an oversight and the publisher would post it to me later."

"No," said Barry. "It wasn't an oversight, it was deliberate. I'm donating the books to you. You don't have to pay anything for them."

"Goodness me," I said. "That's very kind of you. But you didn't have to do that."

"Yes I did," said Barry firmly. "When I was little I used to steal books from this shop. I've felt terribly guilty about that for years. So this is my way of saying sorry, and perhaps of making amends, even though it's probably a bit late in the day for that."

I laughed. "Yes," I said. "I know all about your shoplifting. Once I'd worked out what your favourite kinds of books were, I used to put a selection in a display rack by the door, just out of my father's sight. I thought that would make it easier for you to sneak them out."

Barry was thunderstruck. "You mean you knew all along?" he asked. "And you encouraged me to do it? Why on Earth did you do that?"

"I was paying it forward," I said, "in the hope that one day you'd pay it back. And look – you just did!"

"That would make a nicely circular story," said Barry thoughtfully. He scribbled a note to himself. "I might write that one day." He looked like a huge weight had been lifted from his shoulders. "Now," he said firmly, "let's start signing books, shall we?"

I made a lot of money from that autograph session. Every book I sold was pure profit, of course, and I sold a lot of them. Barry was a very popular writer. That single session more than made up for the losses my father had had to absorb all those years before.

And Barry did eventually write the story. You've just read it...