IT IS undoubtedly York, but a York that very few alive today will have seen. Our main photograph on these pages was taken in about 1900. Pavement stretches off into the distance, not that different from the Pavement we know today, and the building on the left of the photograph is recognisably the building that now houses Marks & Spencer – just look at freelance photographer Mark Sunderland’s modern-day picture of the same scene below if you don’t believe us.

But where today Piccadilly cuts away to the south, with Lloyds Bank on the corner, in 1900 Pavement just continued serenely on its way. There was Melias Tea Stores, a shop advertising Tadcaster Ales and Stout and, front of picture, Isaac Poad and Son, corn and potato merchant.

The juxtaposition of these two photographs, old and new, is a timely reminder that, even in a historic city like York where many of today’s streets follow medieval street plans, there have been significant changes even in comparatively recent history.

It is local historian and bookshop owner Paul Chrystal whom we have to thank for thee images, and the others on our centre spread today. The 55-year-old runs the Knaresborough Bookshop in – guess where? – Knaresborough. But in his spare time he has developed something of a sideline: producing, in partnership with Mark Sunderland, fascinating local history books which match old photographs with modern pictures showing more or less the same viewpoint.

Paul and Mark have already been responsible for producing Villages Around York Through Time and Knaresborough Through Time. York Now And Then, from which all today’s photographs come, is their latest collaboration.

Paul, who lives in Haxby, admits he came to writing local history books quite late in life. Now 55, until three years ago he had spent most of his career in medical publishing: working in sales for a publisher which sold medical books to Europe and the middle east.

Then, three years ago, the married father of three developed heart problems. In 2007, he went into hospital for a triple heart bypass, and he decided it was time for a change of career.

He left the medical publisher, looked around for something to do, and bought the Knaresborough Bookshop.

“I had the triple heart bypass in September, 2007,” he says cheerfully, “and took over the bookshop in November the same year.”

He enjoyed running his own bookshop, but found the life a little quiet. “I thought ‘I can’t just sit here reading stock all day’,” he says. So he contacted a few publishers with an idea for a book of local history which juxtaposed old and new photographs – and he was away.

He has been steadily amassing a library of old photographs ever since, borrowing some from friends and acquaintances, but buying the rest, at auction or on eBay.

Once he has decided which old photographs to run in a book, Mark goes off to recreate the picture as closely as he can, while Paul settles down to the research. “I do quite a lot of it online when I’m in the bookshop, but I also visit libraries, the Borthwick Institute, and I buy a lot of books to do the research.”

Doing a book about York posed its own challenges, he admits, because some of the city’s streets haven’t changed that much. “Quite a lot of things have stayed the same, and always will do.”

But enough streets, and enough shopfronts, have changed to make such a book endlessly fascinating to those who know and love York. Sometimes, even where the buildings themselves are more or less the same, the clothing the people in the old photographs wear, or the old cars or horse-drawn vehicles in the streets, give an oddly exotic look to streetscapes that are essentially familiar.

Some of the most striking photographs in York Then & Now involve the city’s rivers, however.

The Marygate Landing in Mark Sunderland’s modern photograph is instantly familiar to anyone who knows the city today, but how different it is in the old photograph.

Paul doesn’t have a date, but he believes the two boats – sailing barges – are unloading coal on to the horse and cart for onward delivery.

The Ouse has been vital for transport of freight through much of York’s history, from the earliest times right through the Roman and Viking occupations to the Middle Ages, the industrial revolution and the Victorian age.

Today, the river remains busy – though “the commercial river traffic has been replaced by pleasure boats and canoes”.

• York Then And Now by Paul Chrystal and Mark Sunderland is published by The History Press priced £12.99. It is available from most good local bookshops.

• More of Mark Sunderland’s work can be seen on his website at marksunderland.com