“The next step is the most important,” says Smith. “Get your hairdryer and switch it to the cold air setting and blow out those particles from your hair. Those particles absorb the oil and you remove them from the hair by blowing them away and you’re left with this fresh, clean hair.”

Yes, a blow-dryer might add a minute or two to your routine but, in my opinion, making my dry shampoo work harder (or work at all) is worth the quick blast of cold air – especially if it means that you can watch another episode or get a bit more kip without sacrificing a good hair day, too.

Stuck for a decent dry shampoo? I’ve found the most luck with the Amika Perk Up Dry Shampoo, £20 – it sucks up oil and adds the natural-looking lift than can often be lost between washes.

How to use dry shampoo properly: this two-step trick instantly “dry cleans” greasy roots