Real ones, rather than metaphorical.  In less than a month, I'll probably never clap eyes on these folk again, in spite of having shared bits of my early mornings with them for the last half year.  Seems worth recording them, at least a little.  This is not an exhaustive list, naturally!

1. Romford to Liverpool Street

Three-quarters of the passengers on the 4.53 are postal workers, on their way to Farringdon, where there's a big sorting office.  Let us, therefore, begin with:

The Couple

Two male posties (well, maybe just work in the sorting office, hard to know). Always sit together, always walk together.  Stand just a little closer together than mere friends tend to.  Look good together, in fact.  I really do hope they are a couple, they seem to fit.

James Bolam

Very reminiscent, in looks, of the aforesaid actor.  A lined face, showing many past cares, but a look that suggests great laughter in the face of adversity.

Incredible Talking Man and 'Friends'

He talks. That is his nature.  His usual ploy is, on arrival in the carriage, to pounce upon one of his colleagues (postal workers again), sit down next to or opposite them, and begin to talk.  They may be asleep, or be reading a paper or book; it matters not.  If they don't respond, he'll repeat the phrase, with a "hmm?" or a "huh?" thrown in, in an attempt to elicit some reaction.  If they look away, he'll even go so far as to manouevre himself into their eyeline.

Quiet Carriage Man

"THE THING I LIKE ABOUT EARLY TRAINS", he confides to his friend, and thus the entire carriage, "IS HOW LOVELY AND QUIET THEY ARE".