We need to talk about the 'undie tuck' on The Bachelor last night.

Something big happened on The Bachelor last night. And I mean, ‘sent-my-mind-racing-and-kept-me-up-all-night’ kind of big. HUGE in fact.

I’m talking about THAT moment on Alex and Richie’s date the Camilla store. The one where she tucked her dress into her undies… on purpose.

We need to debrief.

The intentional tuck. Image: Ten Play

I thought I knew a fair a bit about styling. I know how to wear a scarf at least six ways, have a decent collection of Hollywood tape and am aware of the wonders a belt can do to an outfit.

But never, ever have I come across the "undies tuck" trick, as demonstrated by the sales assistant, that instantly makes a long maxi dress become a mini. Clearly I'm an amateur. (Post continues after gallery.)

Actually I lie. I've done it once - but it was entirely by accident upon exiting a public bathroom. It took several minutes for me to notice and I was, of course, mortified.

It turns out this styling tip wasn't a sales assistant going rogue to make the most of her 30 seconds of fame on The Bachelor. This is a 100 per cent, genuine alternative way to style your Camilla maxi dress, as advised instore and online.

Richie's reaction just about sums it up. Image: Ten Play

The stunning, floaty dresses cost an average cost of $600, so being able to style it a couple of different ways does make sense.

The execution is relatively simple - put on your chosen long kaftan or dress, then gather up the skirt material at around hip height and tuck into the top of your undies. There's even a handy illustration and video.

But if you thought it ended at the underwear tuck, think again.

There's also the bra tuck, where you tuck the hem of the dress into the bottom of your bra to create a tulip-shaped mini, along with several other styling techniques.

So there you have it. It's a 'thing'. Even if, after all that tucking effort, Alex ended up going for a different dress that was short without any help from her undies.

And next time you walk out with your dress or skirt tucked in your undies? It's fashuun. Obviously.

Listen: We dissect everything that went down in last night's Bachelor episode.

Image: Channel 10.