In general, individual shops have just got bigger and bigger. Until the 18th century they were no larger than domestic room-sized at best, and often were little more than tiny kiosks, less than six feet deep. Trades tend to group together, even today, but then again successful specialist traders often diversify into other goods, so becoming effectively department stores. But it's a cyclical business. W.H. Smith, for example, which started out in 1792 selling newspapers in Mayfair and soon added books, was Britain's first real chain store. The company has done very well by sticking at what it is good at. When it diversified into DIY stores and suchlike, it lost focus. Now, as Morrison remarks, it is back to its core business again. And along the way it has built some very fine shops, particularly the "Tudorbethan" ones of the inter-war years. But typically, Morrison also has a marvellous modernist W.H. Smith to show us, from Eastbourne in 1957.

I know of no other source that can tell you that, for instance, Tesco built 28 new stores in 1991, of which no fewer than 23 had clock turrets - the zenith of the supermarket-as-pretend-barn style. She also shows us a tiny pre-war Tesco shop ("the modern grocers") of the kind you might think the group had long ago outgrown - but no, of course its latest wheeze to build little prefab "Tesco Express" stores of broadly the same size and ambition.

As Morrison remarks, "In the short space of 40 years, the fickle world of shopping had been transformed with greater rapidity than at any other time in history". Note that "had". Because she thinks a new chapter is beginning. No huge new out-of-town centres are being built, the urban fight-back is under way. But she surveys the scene with a Zen-like calm that only someone considering a 1,000 year timespan can achieve. Will online stores destroy shopping? Who knows? We know only that the retail future will be different. She sounds like she's looking forward to it.