But after dismissing the subject in that way, the subconscious mind was still no doubt working at it, for two days later it all at once flashed into my mind that my mysterious young lady was no other than the little Lillian I had known so well eight years before!（A Traveller in Little Things by W. H. Hudson）
英文を前から読んでいくために、語句のかたまりを作ります。こんな具合に課題文をスラッシュ（斜め線）で区切ります（スラッシュリーディング）。語句のかたまりを意識すると、リスニングで英語の意味をつかむのが楽になります。
But after dismissing the subject in that way,／（主語が文頭にないときの主語の前）the subconscious mind was still no doubt working at it,／（接続詞の前）for two days later it all at once flashed into my mind／（接続詞の前）that my mysterious young lady was no other than the little Lillian／（関係代名詞［省略］の前）I had known so well eight years before!
語句のかたまりを前から訳していきます。
But after dismissing the subject in that way,
しかし、その問題をそのように頭から追い払った後
the subconscious mind was still no doubt working at it,
潜在意識は依然として間違いなく考え続けていた
for two days later it all at once flashed into my mind
なぜなら、２日後、〜が突然、頭にひらめいたからだ
that my mysterious young lady was no other than the little Lillian
例の不可解な若い女性は、あの小さなリリアンに他ならなかった
I had known so well eight years before!
８年前に私がとてもよく知っていた
But after dismissing the subject in that way, the subconscious mind was still no doubt working at it, for two days later it all at once flashed into my mind that my mysterious young lady was no other than the little Lillian I had known so well eight years before!
しかし、その問題をそのように頭から追い払った後も、潜在意識は依然として間違いなく考え続けていた。なぜなら２日後、例の不可解な若い女性は８年前に私がとてもよく知っていた、あの「小さなリリアン」に他ならないと、突然、頭にひらめいたからだ！
But after dismissing the subject in that way, the subconscious mind was still no doubt working at it, for two days later it all at once flashed into my mind that my mysterious young lady was no other than the little Lillian I had known so well eight years before!
今回の課題文では、it が２つあります。最初の it は the subject を指しています。では、２つめの it は何でしょう。最初の it のように前を探しても見つかりません。２つめの it は形式主語なのです。
it all at once flashed into my mind that my mysterious young lady was no other than the little Lillian〜
意味上の主語は that my mysterious young lady was no other than the little Lillian〜です。この that節 が all at once と into my mind といった語句にまぎれてしまい、わかりにくくなっています。
動画の後半部分でリスニング用音声が流れます。
