That bulge by your armpit isn't fat. It's your own bust, squeezed out by a bra that's too small at the sides.

You know exactly which bit we mean. The soft pad of flesh that bulges out between the side of your bra and the top of your arm.

It's the reason the sleeveless dress still has its tags on. It's why you lift your arm to wave on the school run and then drop it fast. It's why every photo at the barbecue gets checked for that one angle.

You've probably decided it's underarm fat, and that it's yours to live with. It isn't. And the fact you've been told it is has cost you a lot of summers.

Most women try the same three things. A bigger back size, so it stops digging. A minimiser, to flatten everything down. Or a tight sports bra, to clamp the lot in place.

All three share the same flaw. The cup stays narrow and shallow at the sides. So the bra presses forward on your bust, and the tissue has nowhere to go except sideways, out under your arm.

The harder you squash, the bigger the spill gets. Add a wire digging a red groove along your ribs, a band riding up your back, and straps carving dents in your shoulders, and you're paying in pain for a bulge that's still there.

Your breast doesn't stop at a neat line in the middle of your chest. It runs out towards your armpit. Fitters call it the tail of the breast.

A cup that's too small and too shallow cuts straight across that tail. Whatever doesn't fit gets shunted out the side and sits there looking like a roll of fat. It isn't fat. It's bust that's been pushed out of a cup that was never wide enough to hold it.

Give that tissue a full, deep side to sit in, and the bulge simply goes back where it belongs. No dieting, no arm workouts. Just a cup shaped for the whole of you.

The ShapeChic Original Bra was cut around that missing side. Each lace cup runs deep and wide, with full side panels that reach back to scoop the spill forward and hold it in.

There's no wire, so nothing digs into your ribs, yet it lifts your bust up and forward. Wide, cushioned straps spread the weight so they don't dent your shoulders. And one wide, smooth back panel lies flat, so there's no band riding up and no rolls bulging above it.

No hooks. No clasps. You pull it on over your head like a vest, and everything settles where it should. Sizes S to 4XL, in seven colours.

Put on your most unforgiving vest top. Stand side-on to the mirror. Lift your arm.

In your old bra you'll see it: the bulge over the edge, the strap cutting in, the back band creased into a roll. In the ShapeChic bra the side line runs smooth from bust to arm. The spill is gone, because it's back in the cup lifting your bust instead of hanging under your arm.

Lift up, smooth sides, a flat back. Women tell us they look two dress sizes smaller in the same clothes. Nothing about their body changed. The bra just stopped pushing it out of place.

Picture the next garden party. Sun on your shoulders, a glass of Pimm's in your hand, and arms bare in that sleeveless top you've been saving.

You reach across for the sandwiches without thinking about it. You hug your sister without checking the side. When someone takes a photo, you stand taller and smile, because there's nothing to hide.

That's what it feels like to stop dressing around one bulge. Not a new you. Just you again, before the cardigans took over.

That bulge was never yours to hide. It was a cup too small at the sides, shoving your bust out under your arm.

Every summer you accept it, the vest tops stay in the drawer and the cardigan wins again. You don't have to keep paying that.

Right now it's Buy 1, Get 2 FREE: three ShapeChic bras for the price of one, with free delivery and a 30-day money-back guarantee. Pick your size, from S to 4XL, and choose three of the seven colours. Then try the mirror test yourself.