La Coupole - Post War Investigations

Post War Investigations

Shortly after the Wizernes site had been captured in September 1944, Duncan Sandys, the head of the British "Crossbow Committee" investigating the V-weapons programme, ordered the constitution of a Technical Inter-Services Mission under Colonel T.R.B. Sanders. It was given the task of investigating the sites at Mimoyecques, Siracourt, Watten, and Wizernes, collectively known to the Allies as the "Heavy Crossbow" sites. Sanders' report was submitted to the War Cabinet on 19 March 1945.

The purpose of the Wizernes site had been unclear prior to its capture but Sanders was able to deduce its connection with the V-2 from the dimensions of the complex and some intelligence information that his team had been able to retrieve. Sanders' report concluded that it was "an assembly site for long projectiles most conveniently handled and prepared in a vertical position". He conjectured the approximate length of the projectiles from the height of the Gustav and Gretchen tunnels, though he noted that there was some doubt about the height of the doors at the tunnel entrances. Segments of the doors had been recovered from a storage dump near Watten railway station, but were incomplete. Judging from the size of the tunnel entrance, the maximum size of the projectile could have been between 17 metres (56 ft) and 24 metres (79 ft) in length and 4 metres (13 ft) in breadth. (This was substantially larger than the V-2, which measured 14 metres (46 ft) long and 3.55 metres (11.6 ft) wide.) Two witnesses interviewed by the Sanders team reported "an intention of firing a projectile 18 metres long". Sanders noted that "the dimensions of the site make it suitable for the A.4 (V-2) rocket, but the possibility of a new rocket up to half as long again as the A.4 and twice the weight cannot be ruled out." He concluded that much of the site was becoming unsafe due to the progressive collapse of timbering and recommended that the tunnels and workings under the dome should be destroyed to prevent subsequent accidents or misuse.

The site reverted to private ownership after the war. As the quarry had long since been worked out, it was abandoned. The tunnels were not destroyed but were sealed off, though at some point they were reopened by local people and could be entered; the octagon remained sealed off with a ceiling-to-floor barricade. The quarry itself remained in almost the same condition as it had been in 1944, with sections of railway track still in place on the quarry floor. The hospital section remained relatively intact and was used by the local gendarmes as a shooting range.