This is the cleverest Harry Potter tattoo you'll see all day

'I solemnly swear that I am up to no good'

The era of the Harry Potter tattoo is upon us, an inevitable product of the original Potter fans now being in their twenties and thirties. Fans under the age of 14 might be content with a chocolate frog and the promise of a Warner Brothers Studio Tour, but diehard adult Potter fans prefer something more permanent.

Instagram account @HogwartsTattoo collates some of the most dramatic and elaborate.

There are golden snitches:

There are (many) slightly creepy Voldemort follower Dark Marks:

Some Potter fans have gone for the whole Hogwarts (literally):

But others have been more subtle, proving it's not all giant castles, snakes and skulls:

But a new tattoo posted by this Reddit user blows all other Harry Potter tattoos out of the water. Fans of the book will remember Harry Potter's Marauder's Map, which was given to Harry and used to explore Hogwarts castle without being caught. The Marauder's Map looks like a blank sheet of paper, until of course you tap it with your wand and say the magic words: 'I solemnly swear that I am up to no good.' More from Marie Claire: 8 designs tattoo artists are fed up of being asked to do

In tribute to this, one Harry Potter fan has had a tattoo inked onto their body with the Marauder's Map password. But the best bit? In honour of the map's secret purpose, the line to open it has been tattooed in 'invisible ink' which can only be seen under black light.

Brilliant. And also a rather good idea if you don't want your HP tattoo to be visible during the day. Reddit user, we tip our pointy hat to you.