The look is slinky and sexy this season, but it's also flexible and there are no hard and fast rules. If you want something on a grander scale just make sure the silhouette is simple - frills are banned. Strapless is big news in all styles and essential if you favour the ball-gown look.
If you want to go the whole hog try H&M - it has the best range of big dresses. The frock featured is a real princess number - it has a boned bodice (with detachable straps, in case you're worried the boning won't support you) plus a tulle-layered underskirt, and at pounds 49.99 it's the bargain of the season. At the other extreme, for minimal chic try Warehouse - the grey satin strapless dress shown here would be smart enough for Posh Spice, although you'll need to be as confident to carry it off. If you're more retiring, think about the Giant dress. Its double layers - lace overslip on slinky underslip - hide a multitude of sins and make a sexy alternative to the little black dress.
Finally, underwear: if you go for a strapless figure-hugging number, treat yourself to a strapless bra and g-string. Don't ruin that fantastic frock moment with a stray strap or VPL.
THIS PAGE, CLOCKWISE FROM RIGHT
Raspberry sequin dress (sizes 8-18), pounds 50, Dorothy Perkins, Brent Cross Shopping Centre, London NW4 (tel: 0800 731 8285)
White beaded feather dress (sizes 8-14), pounds 150, Karen Millen, 22-23 James St, London WC2 (tel: 01622 664 032)
Red duchess satin dress (sizes 8-18), pounds 120, Laura Ashley, 256-258 Regent St, London W1 (tel: 0870 5622116). Pink diamante necklace, pounds 12, Warehouse, 19-21 Argyll St, London W1 (tel: 0800 9159902)
Grey lace dress with bead straps (sizes 10-16), pounds 180, Monsoon Twilight, 5 Barkers Arcade, Kensington High St, London W8 (tel: 0171 313 3000). Black sequin mules (sizes 3-7), pounds 55, Faith,
192-194 Oxford St, London W1 (tel: 0800 289297)
Black lace dress (sizes s-l), pounds 75, Giant, Selfridges, 400 Oxford St, London W1 (tel: 020 7255 3007). Black diamante sandals (sizes 3-8), pounds 45, Ravel, 184-188 Oxford St, London W1 (tel: 01458 444712)
Grey crochet sequin dress (sizes 8-14), pounds 100, Nougat, leading department stores (tel: 0207 323 2222)
CLOCKWISE FROM LEFT
Black sequin strapless gown (sizes 10-16), pounds 49.99, H&M, 261-271 Regent St, London W1 (tel: 0171 323 2211)
Grey satin strapless boned dress (sizes 8-16), pounds 60, Warehouse, 19-21 Argyll St, London W1 (tel: 0800 9159902)
Red stretch strapless dress (sizes 8-18), pounds 49.99, Next, 201-203 Oxford St, London W1 (tel: 08702 435435)
Silver dress (size 8-16), pounds 70, Oasis, 292 Regent St, London W1 (tel: 01865 881986). Diamante necklace pounds 10, Warehouse, 19-21 Argyll St, London W1 (tel: 0800 9159902)