For anyone struggling to summon the self-discipline and due diligence to write even one book, a visit to Peter Ackroyd's first-floor Bloomsbury flat could prompt a month's worth of guilty nightmares, the comparison between his workload and those of lesser mortals being so instantly, odiously obvious.

He's sitting in what looks like his library but isn't really: every book on these wall-to-wall shelves is being employed in researching the second volume of his latest venture, which is nothing less than an entire history of England. Before him, beside his computer, sits a long, fat, neat row of books on Charlie Chaplin, which catches my eye. "Oh yes, I'm also doing a short biography of Chaplin. Well, maybe not so short. He's fascinating. I just thought I'd have a go at him."

He's short of time, but still gracious enough to give up 45 minutes. He is 61 now, and a little more tired, though much less emotional, than in a famously bibulous interview with my colleague Tim Adams more than a decade ago. Time, however, has in no way diminished his insane capacity for new projects. And he still springs up with something approaching excitement to show me how his system works. "I don't do it in the British Library or anything, no. I order everything from here – or my assistant does – and then they get labelled, with these little coded stickers. Then I have my little notebooks, and they slowly get filled with references, and each reference is to one of the books as I read them, so when eventually I come to writing I can just flick to one book, one specific little passage, look at it and the surrounding passages, come to my conclusion. That's the idea anyway. These are all" – there must be at least 500 books, each with a small white sticker coded in neat black felt pen – "for the Stuart sovereigns."

Short of time, as we all are, I've only had two days with the proof copy of the first volume, Foundation, and admit I haven't quite finished it, but did manage to get from pre-history to King John. It wasn't a struggle, huge though the book is; Ackroyd's trademark insight and wit, and the glorious interconnectedness of all things, permeate each page. One thing that struck me was the realisation that history isn't nearly as linear as we thought. Something is invented, or discovered, or philosophised, and we tend to think that that's knowledge known from then on, but even in this single volume there are endless forgettings.

"Absolutely," comes his fast answer, spoken, as ever, gently and with a strange mix of confidence and self-effacement. "One thing which most interested me was the fact that neglect, or our genius for forgetfulness, occurs at every level of social and political activity. The same mistakes, the same confusions, occur time and time again. It sometimes seems to me that the whole course of English history was one of accident, confusion, chance and unintended consequences – there's no real pattern."

What he discovered, or rediscovered, is that "what underlines that random happenstance are the deep continuities of national life that survive, uninfluenced by the surface events. In this book, I have little chapters on, say, medieval medicine, or punishment, or medieval humour, simply to convey the broad continuities that underlie this bewildering range of events. Continuities of the soil, the land, the earth." And these help create human – English – sensibilities? "Yes. As I said in my London book, it's a sort of territorial imperative, the landscape; the shape of the geology, almost, has a definite though not comprehended effect on human behaviour, human need. So that's one of the things I was trying to explore I suppose.

Ackroyd has always been fascinated by the telling detail, the tiny sliver of an undocumented peasant's life that brings a whole period into focus. "Also, by the things that don't change. If we were transferred back a century or two I don't think we'd find the excitement or panic or worry or surprise of life any different from the way we do today. Health, money. That's what people worried about in the 14th century as much as today. I find it so much more interesting than the supposed activities of kings, queens, generals. I must say I felt at times I was going to get tired of this endless chronicle of royal and parliamentary battles, but it has to be dealt with in the same way you deal with the more interesting, less sensational matters."

Why, I ask, did he set out on this series? What, in terms of our history, were we lacking? "It just suddenly came to me, as an idea to do; the shape of the six volumes came to me at once; I just wrote them down on a piece of paper. So I've got this one, volume two is the Reformation, three rebellion, four is revolution, five dominion, six innovation. But I don't really know enough about the other histories to know if there's a 'lack', but the same is true of almost everything else I've written. I didn't know how many Dickens biographies there had been, how many books on London, it doesn't bother me. I just want to tell a story."

It's the same driven, headstrong, unapologetic approach he's always taken; he never studied English history, for example, "but then I was never an expert on Shakespeare or Oscar Wilde or Blake or Moore or Dickens or Turner before I started work on them. And then they're gone. None of my books has been ever in my head; after they're finished they go. It's like being a sort of medium; you just grab it when it's there then just release it when it's time to go. There's a lot of instinct, not planning."

Is there one thing that explains how we became so powerful? Island nature? Climate? Invasions? "I don't know the answer to that. By the end of the whole series, I might be able to hazard a guess at some of those reasons. I hope. What I do know is that I've enjoyed it, loved it. I loved, am loving, doing the whole thing. It gave me great pleasure, made me realise it must have been something I'd always wanted to do."

Foundation is published by Macmillan at £25 on 2 September