Fashion flashback to Karen Carpenter and a Paris rainbow

This will go down as the season of the fashion flashback (the 'fashback'?!)

I say this having spent a week going through rail upon rail of high-waisted denim flares, jumbo cords, pleated midis, velvet platforms and - a real blast from the past - baby-grow jumpsuits (remember them?) previewing new collections poised for delivery to department stores and boutiques.

Of course, being talked through all these by some gorgeous 20-year-old public relations girl oblivious to the fact I am confronting the clothes of my youth helps me put a new slant on what I might otherwise consider simply "old".

Take stirrup pants. Back in the 1980s when stretchy, tapered trousers with the foot bit cut out were called "ski pants", we wore them with a shirt/leotard hybrid called a "body".

When I interrupted one blonde pony-tailed PR (with nails painted the exact dark blue I chose as a teenager) to tell her this she replied curtly: "Pay attention."

I'm glad I did. What she said next is vital to anyone experiencing a flashback every time they open a magazine in the months ahead: "Stirrup pants are worn with a leather sweatshirt in 2011."

A leather sweatshirt. Just remember this: what you choose to wear with items making a return to the fashionable wardrobe will mean the difference between looking hip or looking like you're trapped in a time warp.

It's strange. The autumn/winter 2011/12 collections from trailblazing designers such as Marc Jacobs and Prada all managed to look highly contemporary on the catwalk, despite consisting of items cherry-picked from various easy-to-define fashion eras.

The key style of the cult denim brand, Mother, for instance, is the ubiquitous 1970s shape: flares. This season's colours - burgundy/oxblood, gold/saffron/mustard and dark evergreen - are also throwbacks. As is the fabric now making a comeback: velvet.

A modern way to wear this is via footwear. The high street brand, Office, has done a fabulously contemporary wedge velvet "flatform", which, along with Topshop's Doc Marten or Penelope Chilvers's Cuban-heeled ankle boots, could instantly update your wardrobe. Another Chilvers offering is the essential new flattie: the gentleman's velvet crested slipper.

How well I remember wearing this around 1986 with a Rifat Ozbek embroidered jacket (and in my dreams, an Azzedine Alaia dress).

After an absence of I don't know how long, I'm reading about Rifat Ozbek and Alaia again. Not only back by demand, but having survived long enough to see their particular signature being paid homage to by their peers.

Kate Winslet's dress by Victoria Beckham, worn to the Venice Film Festival, was very Alaia with the addition of this season's midi length (his original 1980s style would have boasted a way-shorter hemline).

Some designers seem to master the juxtaposition of old and new effortlessly. Others fail. Christopher Kane's print of crochet squares (crucially fashionable in the early 1970s), which appear on his leather pencil skirts and biker jackets, exemplifies the former category. Christopher Bailey's nod to 1960s shapes for Burberry works because he has learnt that when it comes to design, nostalgia should be sprinkled like salt: sparingly.

It will be interesting to see what, if any, eras come up in the next round of spring/summer shows. Designers delight in throwing the fashion press off scent rather than announcing the comeback of a decade with a fanfare as you might imagine. But there are exceptions.

My most memorable show occurred on the very last day of one particular Paris ready-to-wear season in the late 1990s, by which time the entire audience was tired and homesick, having been away for almost two months, watching fashion shows day in day out.

The decision by the ever-thoughtful Japanese designer Junya Watanabe to accompany his collection of futuristic pieces made in industrial waterproof textiles with a Carpenters soundtrack had the North American contingent weeping - in a nice way.

What at first appeared to be a crazy contrast - models walking to the distinctly melancholy acoustics of Karen Carpenter singing her classic, Rainy Days and Mondays - eventually made sense.

Watanabe's starting point for the collection was a raincoat worn by Ali MacGraw in the 1970 film, Love Story. There was a 1970s feel to the collection but this almost didn't matter. The sheer abnormality of hearing a guilty-pleasure song at a fashion show (where music is so low key - or weird - you rarely register, let alone remember, it) sent one plunging into thought. Songs are soundtracks to our lives but they aren't the only things to evoke precious memories. Clothes do this, too.

Post-show, spilling out of the darkness on to the pavements of bustling Paris, a rainbow appeared in the sky. This remains my favourite fashback.