For context, everything here is Pancras, London, England.
I have an ancestor (Harriet Deady, formerly Thompson, originally Gammon, my 2nd g. grandmother from Halifax, Nova Scotia, British North America) that I am confident remarried after her husband (Richard Thompson, my 2nd g. grandfather) passed away in 1898. She is present on some other contemporary records, has identical particulars, and I can find her in the 1911 census living with her new husband (John Deady), and the length of marriage as given suggests they married around 1905.
However, there is no record of any marriage in the BMD indexes. I have placed a search-based order with the GRO hoping they would search the actual records, but I've just been refunded, so presumably they're not in there at all.
John Deady was born in India but signed up to the Army at 14, and ended up in England by the end of his service in 1900, and was working as a railway porter in 1911. They lived in housing around Euston station in 1911, so I doubt they would have had the sort of money required to travel. Can't rule it out, of course, but I think it unlikely.
Does anyone have any suggestions on avenues I can explore to prove this marriage took place?