A secret underground military complex abandoned by the Nazis as allied forces stormed Normandy after D-day has been found by an English amateur historian.

Gary Sterne came across the series of bunkers that had lain untouched for more than 60 years after buying a second world war map from an old American soldier. Armed with his map he visited the area near the Normandy beaches of Utah and Omaha, where he found the entrance to the military complex hidden under bramble bushes. He was astonished to discover a labyrinth of bunkers, control rooms and equipment abandoned by the Germans.

Mr Sterne, a collector of military memorabilia, said he had been intrigued by the idea of a hidden complex after buying a 1940s German army map from a former US serviceman. He said he had no real idea what he was looking for when he visited the area detailed in the map around Grandcamp Maisy in Normandy.

"I didn't know where I was going but I started to walk across the field when suddenly I found myself walking on concrete," he told Ouest France newspaper.

"I followed the concrete right up to the edge of some trees and it was there I suddenly found the entrance to the underground block, then a tunnel, an office, a supplies warehouse, general quarters, a radio room, other blocks and, most importantly, a room with supports for 155mm guns," he added. "It even had an underground hospital. The Germans had left behind many personal possessions."

The complex is believed to be the most important of German defences constructed during the second world war.

Historians are now examining the site, which has been bought by Mr Sterne, who intends to turn it into a tourist attraction.