Thought being drenched in freezing water for charity was hellish? Well, steady yourself, because there's a new social media charity craze (or SMCC) on the horizon: #WakeUpCall.

And, in the manner of March's No Make-up Selfie mania, you'll need to step away from the bronzer for this one.

A slew of celebrities - among them, fashion faces Naomi Campbell, Daisy Lowe and Laura Bailey, along with ELLE cover man Tom Hiddleston - are backing the new initiative to raise money for UNICEF's charity efforts in Syria, posting pics of themselves having just woken up and adding the #WakeUpCall.

As with any good SMCC, the deal is that you post, donate and nominate - three people, in this case. 

It's the brainchild of UNICEF Ambassador Jemima Khan, who kicked off proceedings by posting a wild-haired, open-mouthed selfie on Instagram.

'I had this idea to try to replicate the astonishing success of the Ice Bucket Challenge, which raised $100m for the previously little-known Amyotrophic Lateral Sclerosis (ALS) Association, and the No Make-Up selfie, which raised £8m in six days for Cancer Research UK,' she told the Daily Mail.

'Thankfully UNICEF –  who I have been working with for 13 years now as an Ambassador - liked the idea and went with it. There are currently 6.5 million Syrian children who are in desperate need of help.

Those essential details? #WAKEUPCALL #UNICEF Text SYRIA to 70007 (to give £5) or http://wwwwakeupcall.org.uk.

See you in the morning...