In 僕の愛したジークフリーデ, by Matsuyama Takeshi, I found this sentence:
すでに手勢はなく、頼みのファーレンベルガーも退場した。ことこの場に至っては『彼女』は一人の非力な少女にすぎない
The main character just arrived with her companion in the presence of the queen, having defeated her soldiers and Farenberga.
It's not the first time I see こと at the start of a sentence, but I'm not sure how I should read it; I tried looking on dictionaries for meanings of the word, and doing a search here, but to no avail.
My best guess is that, at least in this case, it should be read like (という)こと(は), so the sentence translates something like "There weren't any more soldiers, and also the trusted Farenberga was defeated. That meant that at this point [or "place", but I don't think 場 refers the the physical room] she was just a powerless girl", but I'm not sure this is the right meaning.
Is my guess right? Can a starting こと have other meaning?