Lemn boards the Caledonian Sleeper, leaving London at the same time as Auden's Down Special mail train would have departed.
There is no mail on board, but the workers and passengers carry their own delicate cargo of hopes and recollections with them.
Lemn meets a man who spent 30 years working on the travelling post offices, on which the freezing conditions and the long hours were not as poetic as Auden suggests.
But is there a stanza to be written about the lot of the modern rail workers?
Arriving at the busy interchange at Crewe, Lemn talks to the people who catch and dispatch the trains.
Some are in love, some are in therapy and some are in drag.
In the GPO's Night Mail film, the train picks up mail at Carnforth Station in Lancashire.
Ten years later, the same station provided the backdrop for the film Brief Encounter.
Does passion still linger beneath the station canopy?
Lemn's journey is complete, but will a dawn arrival at Glasgow help him finish his poem?