Inversion

Czy mogę prosić o wyjaśnienie:

Only after shehad left for the airport did she remember that her passport was still in her desk in the study.

Only after I started to write the letter did I realise that I had lost their address.

Dlaczego w 1. zdaniu jest Past Perfect a w 2. Past Simple?

2 ja bym tlumaczyl to tym, ze past perfect uwypukla najwczesniejsza czynnosc (had lost)