It would be safe to say that the majority didn't see that one coming! Here's a selection of what the press thought about Maiden's Brit award...

"Amidst all the furore of the Brits there was one very significant - and might I add long-overdue -- winner. For thirty years this band have consistently sold millions of albums, had top twenty hits and a number one, and toured to ever-expanding venues. Currently they're packing out stadia in everywhere from Brazil to Bangalore; songwriters and musicians of the highest strata and they deserve every bit of respect we have." - THE FLY.CO.UK (read more)

'Why Iron Maiden Should Close Next Year's Ceremony'
"Think about: a medley of Howitzer-heavy anthems to close the night -- 'Run To The Hills', 'The Trooper', 'The Number Of The Beast' -- accompanied by a colossal Eddie stalking the stage, eyes ablaze, spitting fire into the first five rows. It'd be an extraordinary, exhilarating spectacle -- and just the thing to shake the BRIT Awards out of the bloodless, self-satisfied torpor into which it seems to have settled." - NME

"Perhaps the most unexpected winners of the night were Iron Maiden - not normally accustomed to Brits success - who were awarded the title of best live act, a category voted by the public. Even show co-host James Corden admitted: "Iron Maiden, who'd have thunk it?" " - Q

"In a renaissance in heavy metal music, Iron Maiden were named Best British Live Act, 29 years after they released their first album." - The Times 

Metal Hammer - 11 Reasons Maiden Deserved Their Brit

MusicRadar - 10 Reasons Maiden Deserved Their Brit