A dark and moody ad for sportswear brand Under Armour has been the most shared ad of the Rio Games despite it being almost six months old, while it never even mentions the Olympics. However, it also happens to star (a bearded) Michael Phelps which has probably had a lot to with its popularity.

The ad shows Phelps’ (who snared his 23rd gold medal in the Rio pool) gruelling training regime under the tagline “It’s what you do in the dark that puts you in the light”.

Check the ad out here:

The ad has had over 10 million views on YouTube and is reported to be the fifth most shared Olympic ad of all time. And it’s proven a triumph for Under Armour not only in brand awareness but in sales too.

The fact that it’s been so popular with Olympic fans has proven a marketing triumph. Brands that aren’t official Olympic sponsors (which Under Amour isn’t) aren’t allowed to mention the Olympics or mention an athlete’s performance for any sort of promotion (known as Rule 40).