On June 18, 1945, George Clutton of the British Embassy, Stockholm, wrote a report on the German concentration camp Ravensbrueck, in which he describes how the Nazis operated a sort of gas train:
"There seem to have been two gas chambers at Ravensbruck. [One] was situated next to the crematorium outside the boundary of the camp and was a small brick building with the appearance of a washroom with showers. It took one hundred victims at a time. The existence of the second gas chamber was widely believed, but no one had ever seen it. It was said to have been brought to have been brought to Ravensbruck at the end of 1944 by S.S. Obsersturm [sic] führer Brauning from Auschwitz where he had been in charge of gassing methods. It consisted of what appeared to be two covered railway waggons attached together and connected with two railway tankers containing the gas. The women put into the trucks were unaware of the fate in store for them and were generally under the impression that they were to be removed to another camp. The doors of the waggons were shut and the gas pumped in at either end from the tankers. Death was stated to have taken two hours."
Clutton explained in his report as to where his information originated:
"I have the honour to report that, in the company of your [Victor Mallet, the British Envoy to Sweden] Assistant Military Attaché, Lieutenant Colonel E. B. Butler, I proceeded by air on the evening of June 5th to Gothenburg to visit the British subjects who had arrived in Sweden from concentration camps in Germany. I spent Wednesday, the 6th, and Thursday, the 7th, seeing them at a Hostel in Hindås where most of them were congregate and also in Gothenburg. On the 7th some of them left by air for the United Kingdom and I had the privilege of saying farewell to them at the airport. The purpose of the visit was in the first place to greet them on behalf of yourself and His Majesty's Legation and secondly to gather evidence regarding cases of deaths of British subjects in the camps from which they came. In accordance with Foreign Office telegram No.725 of 10th May, I also endeavoured to collect as much evidence as possible relating to the general administration of concentration camps and the policy of extermination pursued against the inmates. Colonel Butler in addition was particularly interested in tracing certain female personnel of his organisation whom his Headquarters believed might at one time have been in Ravensbruck. I returned to Stockholm on the morning of Friday, the 9th.
2. The background to the story of these refugees was already known to me from information I had obtained from refugees of various nationalities in Stockholm as well as from retorts from His Majesty's Consul General at Gothenburg, the British Consul at Malmö, the Swedish authorities and the World Jewish Congress. The task before me was therefore to piece together and construct into a coherent whole the disjointed evidence that [was] already obtained with any fresh information available. The fact of [sic] all the British refugees had been assembled together in one place afforded an admirable opportunity of doing this. One of the difficulties in interrogating refugees from concentration camps is that as a result of their sufferings their memories have be affected and dates and names often fail them. To overcome this difficulty Colonel Butler and I adopted the method of interviewing witnesses we knew had the most evidence to give and supplementing this by discussion afterwards with the whole assembly of refugees. We found that three or four refugees together could often supply a name which one alone could not do. The mention of a name or an incident in front of the assembly would frequently produce a string of further names and incidents that had slipped the memory of the individual witness."