Mankin was one of the pioneers of natural fabrics; the fad for ruching and tasselling brightly coloured chintzes and satins into elaborate swags- and-tails and Austrian blinds completely passed him by. His fabrics - traditionals like ticking, canvas and gingham - have understated class. "I'm not a fashion person," he says. "We're about style and substance. I've done the same thing since I opened - I've just refined it. But many of the original materials I sold back then are still here."
His new book is called Natural Fabrics, and the shop is a cornucopia of them. But while he has hundreds of different bolts of material all packed into one small emporium, the effect on the eye is harmonious - even though, as he says, nothing actually matches. "I don't produce co- ordinated ranges - there is nothing cutesy or twee here. But even the materials that are produced from different mills or in different countries go together." To prove it, he hurries to compare swatches and bolts of fabric against one another - it's true, they do blend happily together.
Natural does not necessarily mean neutral, although one of Mankin's newest lines is a range of heavy, cream, jacquard fabric embossed with selections of leaves and fruits rather than the traditional, dense, flowery pattern. His canvas weaves, repps and herringbones, calicos and tickings come in dozens of shades - jade green, deep blue, plum, mustard - but all are sumptuous rather than strident. "We do checks, stripes, plains and that's all. It's amazing how much they can vary. There is a strong vogue for bright colour at the moment, and we've had to get some bright colours in," he says, pointing out some tickings striped in mango or pink or crimson, "but I think they'll disappear within 18 months or so." As well as colours, texture is important - particularly for fabrics left undyed. There are chenilles, chevron weaves, textured stripes in different weights. All the fabrics have been names "with an English ring - Cricket Plaid, Wessex Check".
Mankin has worked with materials all his life; his mother was a fine- quality dressmaker and his father's business was textiles and trimmings. He studied at the London College of Fashion, but was interrupted by National Service. "When I came back I didn't feel like sewing. I drifted into my father's business first of all, then into working in the leather trade - you can't get more natural than that. All my linings were cotton, the fittings were brass, buttons were horn - I've still got the horn buttons on my suit."
The recession claimed his leather company and he moved over into natural fabrics, but his first excursions into the field were an economy measure many years before. "My father sold fabrics and one of them was linen scrim - marvellous stuff for polishing, window-cleaners used to use it. When I got my first flat, I was about 23, I made the curtains out of it - in those days it was about 30p a metre. These days it's not about cheapness, it's about the look. If you want to go for the look, you've got to be generous - cheap materials are very thin. It's easy to keep prices down by cutting quality, but I'm very much into quality." With a heavy calico, he says, even the dreaded Austrian blind can look good: "You get a wonderful sculpted look."
Today, he sources his materials from English and Indian fabric mills. "Look at this, it's Jermyn Street shirting, though you won't find it in Jermyn Street now," he says, pulling some soft, checked material from a cupboard, in glowing shades of red-and-white or blue-and-white check. "It would make wonderful curtains, or duvet covers, or pillowcases. It's from the last mill in England that makes these very super-fine poplins - very English. Our Indian materials are also very fine quality - I have them all finished in this country."
Mankin's book suggests curtains, cushion covers and loose covers, blinds, seat covers and pillowcases to make, as well as using the materials for upholstery. One of the greatest advantages of the natural look is that it fits everywhere. "My fabrics have been featured in very modern and very antique homes, and they worked in all of them, because they're so classic - completely timeless."
Natural Fabrics by Ian Mankin is published on 1 May by Ebury Press, pounds 17.99.