[Waley 訳]

At the court of an Emperor (he lives it matters when) there was among the many gentle women of the Wardrobe and Chamber one, who thought she was not of very high rank was favoured far beyond all the rest;

[Seidensticker 訳] 

At a certain reign there was a lady not of the first rank whom the emperor loved more than any of the others.

[余談] 

 ”いとやんごとなき際にはあらぬが” の ”が” は主格の助詞である。小学館「日本古典文学全集」にははっきりと注釈に記してある。

詳しくは大野晋他編『岩波古語辞典』の巻末「基本助詞解説」にあたるがいいが、大野晋『古典文法質問箱』（角川文庫）がわかりやすい。