Almost every disappointing evening bag purchase comes down to a phone. A large phone is around sixteen centimetres long and eight wide, and a great many small clutches and minaudières are shorter than that, which means the bag simply does not close. The number to look for is an internal length of at least seventeen centimetres, and rigid shapes need it exactly since they cannot flex. After that the list is short: a card, a key, a lipstick. Anything more and you are looking at a small shoulder bag rather than a clutch. It is worth deciding which of the two you want before shopping, because a clutch occupies a hand all evening while a bag with a strap does not, and that single difference matters more over four hours than the design does.

A rigid minaudière or box clutch protects its contents, stands on a table and is the most formal option, and it holds almost nothing and cannot be squeezed. A soft clutch in satin or leather flexes to take one more item, folds under an arm and creases with use. A tiny shoulder bag is the most practical of the three and the least formal, and a detachable strap gives you both options in one purchase. The closure is worth checking with a phone inside, since a magnetic clasp on a full bag will pop open in a crowd and a frame clasp will not. On material, satin marks with water permanently, metallic leather scuffs at the corners, and a plain smooth leather or a beaded surface is the most durable across several seasons.

We have settled on one small shoulder bag with a detachable chain in a neutral metallic and stopped buying clutches almost entirely, on the grounds that a bag which frees a hand is worth more at an event than one which looks marginally better in a photograph. If a clutch is the only right answer for an outfit, we choose a soft one over a rigid one for the extra centimetre of give. And we test the closure at home with everything inside. If you take one thing away, measure your phone against the bag's internal length before buying, because it is the single most common reason a beautiful evening bag never gets used.