Were someone to ask you what the dress of the season was (I know - suspend your disbelief here, for in Fashion Land, these questions do pass for intelligent conversation), you would probably name the ones you'd seen being worn the most.
It would be Stella McCartney's floral chiffon dress, or, on the high street, that cherry red tea dress by Kate Moss for Topshop.
It would not, it's fair to say, be a short-but-not-too-short, sweet-but-not-too-sweet dress whose only defining characteristic is that it looks pretty bloody unremarkable. And yet the Lucky is undoubtedly the dress of the season so far.
This is because sometimes a girl doesn't want an all-singing, all-dancing dress in the latest hot colour or print. Sometimes, a girl just wants a dress that will make her feel brilliant.
And such is the brilliance of the Lucky that it has been worn by such diverse women as Scarlett Johansson, Hilary Swank, Sex and the City's Kristin Davis, model Alice Dellal and Kate Middleton, all of whom have found this shortish, sweetish dress to be the last word in chic.
Part of its appeal is surely its versatility: it can take the wearer from day to evening with all the insouciance that only a very cleverly designed dress has.
'I called it the Lucky because every time I wore it, something amazing happened,' says Daniella Helayel, its designer. 'I wore a white one to almost every party last summer, and women would always come up to me and ask me where they could buy it.'
As the owner and designer of Issa, Brazilian-born Helayel has a bit of a track record when it comes to dreaming up It dresses: her soft jersey wrap dresses have long been a wardrobe staple among the well-heeled of west London, with fans including Laura Bailey and Madonna.
For the Lucky, she was inspired by a vintage baby's dress - which explains the puff sleeves and the innocent, girlish feel. It first appeared in Issa's spring 2007 collection in black cotton with a sheer back (the version of choice for both Johansson and Middleton), alongside two closebacked versions in white and red. It proved so popular that it is now reissued every season.
'I think the Lucky is such a hit because it flatters every body shape,' says Helayel. 'I started designing dresses because I couldn't find any that suited my own body - I'm Brazilian and curvy. The Lucky suits me but it also seems to suit more slender figures. It just seems to be one of those dresses that everyone feels good in.'
The bad news is that you'll be lucky to bag a Lucky at all this summer. The dress is currently sold out, although all three colour-ways are being reissued for autumn, along with a new version in denim (£323), which should be hitting stores in two weeks' time. Harrods currently has a waiting list - but if you join it soon, you might just get lucky yourself.