Right, I’m here to tell you what the fashionable summer dress you need to buy this year looks like. I’m about to lay down the law on whether rose prints are more on trend than forget-me-nots, and explain whether a bell sleeve or a trumpet one will hoist you up the best-dressed lists. I’m going to map out those postcodes in which a cold shoulder is still de rigueur and those neighbourhoods in which you must switch to a kimono sleeve. And, after that, I’m going to explain how to break into your own house at the end of the night, if you are unable to take your keys out with you because they don’t fit into your on-trend miniature circular basketweave clutch bag.

Or none of the above, actually. I’m here to help you find the perfect summer dress, which is absolutely not the same thing as the most fashionable one. The search for this dress transcends fashion for the simple reason that the perfect summer dress is an almost holy object. The days on which this piece will be worn are the most precious of the whole year, and that makes the dress itself a kind of talisman.

There is something nostalgic at the heart of how we think of summer. The summers of long ago stretch out and warm up as the photographs fade, becoming balmier and more lazy in memory than in reality. Nostalgia never goes out of style, so being on trend really isn’t the be all and end all. And besides, many of the best bits of summer are not particularly fashion-forward. There is nothing cool about most weddings, but they are still almost always brilliant: the fact that the bridesmaids are in lurid mint green won’t stop you welling up. There is nothing modish about following a pub garden dinner of beer and salt and vinegar crisps with a cup of tea and two rounds of toast and Marmite munched standing up in the kitchen when you get home, but it remains a stone-cold classic al fresco dining scenario.

Star turn: Rixo’s constellation print.

I am a fully paid-up devotee of erring on the side of overdressed rather than underdressed, but that doesn’t mean you always have to be edgy. There is something a bit naff about trying to be cooler than the party you are going to. Much better to be the most fun guest at the wedding, the one still twirling baby bridesmaids around the dancefloor at midnight, than the one whose day peaked with the 11am mirror selfie of her outfit.

The most successful summer dresses I’ve bought recently have been lightweight but with sleeves and a long hemline. There’s a dark Rixo one with a constellation print, below the knee, but with subtle, thigh-high splits in the skirt; and a Boden one in rose pink that has singlehandedly converted me to ankle length, because it makes me feel serene even when it’s 27C on the bus. I feel carefree, rather than exposed. They are cool on a hot pavement, but I don’t get goosebumps under air conditioning. I find they work best in a strong colour and/or print; the ethereal white-nightie vibe makes me feel a bit silly – though it looks charming on lots of other people, so each to their own.

Our edit of this summer’s best dresses includes stripes and leopard print, polka dots and florals. There are Bardot and bateau necklines. Choose from short hemlines or long – or plump for dipped, if you can’t make up your mind. These are not just frocks of the moment, but dresses you will return to next summer, and the one after that. Sustainability, after all, isn’t just a trend. Which one’s your favourite? Answers on a postcard, please.