Suspect: John Langan (dates unknown)

I've been waiting for today to post things on this man, who I think is one of the more interesting suspects due to some bits of coincidence, or perhaps not. After the murders of Elizabeth Stride and Catherine Eddowes on September 30, police in France arrested a vagrant named John Langan (Langran in some communications) who could also give no reason for his being in the French port.

It was noted by E.W. Bonham that Langan bore a resemblance to certain sketches of the Ripper made based on witness descriptions, and so he brought the seemingly unrelated arrest to the attention of the Home Office. Interestingly, Langan revealed that he was American, and that he had no desire to be sent to England, but that if arrested he wished to be sent to Cardiff, Wales to work in coal mines. Under questioning, he revealed that he had been to Wales ten months previous, after which he returned to America.

He claimed that

...when in Wales he lodged with Mrs Davis 30 Dufferin, a village two miles from Merthyr Glamorganshire, that lately he was lodging with John Richmond 47 Castle Street Hamilton near Glasgow, and that when last in America he was employed in some ironworks.

A search of the 1882 census of Britain revealed that a girl named Mary Jane Davies, a widow at the age of 16, was employed at the Brunswick Hotel in Merthyr Tydfil, Wales. This may dovetail with the information provided by Joseph Barnett at the inquest into the death of Mary Jane Kelly:

The deceased told me on one occasion that her father named John Kelly was a foreman at some iron works at...Carmarthen or Carnarvon, that she had a brother named Henry serving in 2nd Battn. Scots Guards, and known amongst his comrades as Johnto, and I believe the Regiment is now in Ireland. She also told me that she had obtained her livelihood as a prostitute for some considerable time before I took her from the Streets, and that she left her home about 4 years ago, and that she was married to a collier, who was killed through some explosion. I think she said her husband [sic] name was Davis or Davies.

Should "Mary Jane Davies" have been Mary Jane Kelly (who would have been approximately 16 in 1882) this is interesting: also assuming the possibility that the "Mrs Davis" of Langan's statement could have been the Mary Jane Davies of Merthyr Tydfil, we must conclude that a suspect possibly with previous knowledge of Mary Jane Kelly bears further investigation.

Scotland Yard released John Langan on October 16. What would they do if they knew that they possibly had been holding Jack the Ripper?