The number of minutes to leave your conditioner in before rinsing for 'stronger, shiny hair'

Offering his top tips for "thicker, stronger, longer and shiny" locks, he shared the ultimate hair-washing routine.

Post-shampooing, he advised women to leave their conditioner in for one to three minutes before rinsing it out.

William told GB News: "I think first on the list to create more beautiful hair is [developing] cleansing and conditioning routines.

"I recommend shampooing your hair no more than three to four times a week so as not to disturb the acid mantle of your scalp. Too much shampooing can cause the hair to become too oily or too dry.

"You want to cleanse the hair as gently as possible while giving it the nutrients that it needs."

He advised opting for shampoos with ingredients such as panthenol, biotin and lotus flower, which can all help create "stronger, thicker and shiny hair".

After shampooing - and most experts recommend doing this twice - it's time for conditioner.

While you likely already use a conditioner during your hair-washing routine, you may not be leaving it in long enough to truly feel its benefits.

William said: "Always follow up with a conditioner for one to three minutes - or a leave-in conditioner can be very beneficial too."

The hair experts at Pantene also stressed the benefits of incorporating a conditioner into your cleansing routine.

They said: "A conditioner is a hair care product used after a shampoo. Apart from ingredients such as silicone, oils and emollients, this moisturising agent also contains cationic surfactants (cleansing ingredients) that get rid of the oily elements in your hair.

"Together with these two powerful factors, a conditioner replenishes the moisture lost during shampooing."

Conditioner also strengthens hair cuticles with a protective coating, preventing breakage and boosting hair growth.

"Another major benefit of using a conditioner is that it moisturises your hair," the experts revealed, "and makes it soft, smooth, reduces frizz and adds shine to your tresses".

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Conditioner should be "gently massaged" into the hair to "ensure that each hair strand is coated well", before being combed through with your fingers. The experts confirmed that it should be left on for a few minutes to "work its magic".

Alternatively, a leave-in conditioner applied to your hair post-shampoo can provide "extra hydration". It is also great for reducing your risk of breakage.

William stated: "One of the worst things for the hair that causes breakage is if you try to comb your hair while it's wet and it has not been conditioned and detangled."

The celebrity hairstylist also spoke to GB News about which hair length is most prone to damage, warning women that they "have to be more careful".