nature of the chalk underground. As a result, pronounced underground warfare had been a feature of the Vimy sector since 1915. In preparation for the Battle of Vimy Ridge, five British tunnelling companies excavated 12 subways along the Canadian Corps' front, the longest of which was in length. The tunnellers excavated the subways at a depth of 10 metres to ensure protection from large calibre howitzer shellfire. The subways were often dug at a pace of four metres a day and were often two metres tall and one metre wide. This underground network often incorporated or included concealed light rail lines, hospitals, command posts, water reservoirs, ammunition stores, mortar and machine gun posts, and communication centres. Lieutenant-Colonel Mike Watkins memorial Near the Canadian side of the restored trenches is a small memorial plaque dedicated to Lieutenant-Colonel Mike Watkins MBE. Watkins was head of Explosive Ordnance Disposal at the Directorate of Land Service Ammunition, Royal Logistic Corps, and a leading British explosive ordnance disposal expert. In August 1998, he died in a roof collapse near a tunnel entrance while undertaking a detailed investigative survey of the British tunnel system on the grounds of the Canadian National Vimy Memorial site. Watkins was no stranger to the tunnel system at Vimy Ridge. Earlier the same year, he participated in the successful disarming of 3 tonnes of deteriorated ammonal explosives located under a road intersection on the site. Visitors' centre The site has a visitors' centre, staffed by Canadian student guides, which is open seven days a week. During the memorial restoration, the original visitors' centre near the monument was closed and replaced with a temporary one, which remains in use today. The visitors' centre is now near the preserved forward trench lines, close to many of the craters created by underground mining during the war and near the entrance of the Grange Subway. Construction of a new educational visitors' centre is expected to be completed by April 2017, in advance of the 100th anniversary of the battle. The new million visitor centre is a public-private partnership between government and the Vimy Foundation. In order to raise funds the Vimy Foundation granted naming rights in various halls of the visitor centre to sponsors, an approach which has met some level of controversy due to the site being a memorial park. Sociocultural influence The Canadian National Vimy Memorial site has considerable sociocultural significance for Canada.