The indie rock favourites have enjoyed a meteoric rise since first stepping onto the historic courtyard stage as support artists for Blondie and then returning to open for James last summer.
Since then, they have topped the official albums chart with their second album Pretty On The Internet and cemented their status as one of the UK's most exciting live bands.
Speaking backstage with BBC Radio 6 Music's Chris Hawkins ahead of the show, frontman Jamie Boyle reflected on the band's rapid ascent.
"Is it only a year ago? That's crazy. I feel like we've been looking forward to this for ages, because we knew about it then,” he said.
"We found out that night that we were going to headline, and it feels like it was forever ago.
"It's mad that it was only a year, but we're here!"
The K's made every second of last night’s show count, delivering an explosive set packed with fan favourites including Icarus, Before I Hit The Floor, Chancer, Gravestone, The Bends (Here We Go Again) and Heart On My Sleeve.
Highlights from their chart-topping album Pretty On The Internet followed, with Landmines, Hometown, Perfect Haunting, Lights Go Down and Rat Poison.
The K's brought their debut headline show at the venue to a triumphant close with Sarajevo, TV and Dacton & Wanderella.
Before the finale, Boyle told the packed courtyard: "Thank you for tonight Piece Hall. It's just as beautiful as we remember."
Opening the show was indie outfit Lady of Mars, followed by rising North East singer-songwriter Tom A. Smith.
Live at The Piece Hall tonight with Scissor Sisters and several more acts before the end of this month.
Photos courtesy of Cuffe and Taylor and The Piece Hall.
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