Iron Maiden's beer The Trooper has sold over 20 million units in over 50 countries ever since its introduction to the world in 2013. Since then, Iron Maiden has rolled out more themed beers alongside Robinsons Brewery. Now the band is returning to their roots.

Iron Maiden has officially announced Trooper Nitro, which is a keg version of The Trooper, but charged with nitrogen and Co2. Here's how Trooper brand manager Sam Kennerley explains it.

"Our keg version of Trooper has been extremely popular, but after listening to feedback from our customers and numerous on-trade trials, which had outstanding results, we decided to switch to mixed gas. The result — an awesome longer-lasting keg-conditioned Trooper ale whose deep and complex flavor has been enhanced with a cooler temperature and a perfect serve."