Tattooing is an art form like no other. To use the human body as a canvas for art was once considered to be anomalous, rebellious and borderline wacky, especially given the element of self-inflicted physical pain that comes with getting a tattoo.

But in the U.S. alone, nearly 45 million people have at least one tattoo, including 40 percent of adults ages 26-40. In the UK, roughly 1 in every 5 people is tatted. The most interesting part about these surprisingly high numbers? You might never guess that many of these people have tattoos.

London-based photographer Alan Powdrill reveals “the secret lives of tattoo fanatics” across the UK in his series, Covered. His subjects, ranging from ages 23 to 66, were first photographed fully clothed. For instance, here’s a mellow-looking gentleman named Graham:

Then, Powdrill had them strip down. Here’s Graham beneath his work attire:

Incredible, right? Not only do you see Graham in a whole new light; you also see the astounding artwork he has dedicated his skin to. Strangers don’t know this Graham. They don’t know that pretty much every tattooable inch of his body from head to toe is bursting with color, nor do they know that this man has sat through hours upon hours of pain and spent thousands of dollars to express himself.

"I was 51 when I started," Graham told Powdrill, "and my dad was already dead and my mum didn't say anything, as she was in the early stages of dementia."

Powdrill’s other subjects are equally fascinating. Here’s Chris, 25:

“If I ever forget who I am, I take my clothes off and look in the mirror and find out who I am again,” Chris says.

Powdrill told Quartz, “The method of double portraits with & without clothes was inspired by a famous Helmut Newton series. It helps highlight ‘what lies beneath’ and our perceptions of the people we’re looking at.”

This series goes to show that you truly cannot “judge a book by its cover.” Check out a few more images from Covered below, and visit Alan Powdrill’s website to see more if his work.