Some people doze on the train on their way to work while others watch the scenery go by or hide behind their newspapers.
A few work, spending their time poring over paperwork or talking on their mobile phones.
However, lawyer Geoff Steward, 30, chose to do something completely different on the early-morning train from Haywards Heath to CityThameslink in the heart of London.
During the hour-long journey to and from work, he scribbled out the bones of a children's book inspired by the memory of his father.
His book, The Lost Grandad, will be launched in the bookshops next month.
Geoff took the idea for the story from a family tragedy, the loss of his father, John, who died in 1998 from a lung complaint following a long illness in his 50s.
Six weeks later, Megan, the first child of Geoff and wife Julia, 32, was born.
Geoff said: "The title of the book derives from the sad fact that Megan was never going to see her grandfather.
"In the book, the main character is a boy who has to use his imagination because he has been told he has lost his grandfather.
"But he takes this to mean his grandfather is merely lost somewhere and the more he uses his imagination the more he gets to know him."
"Before Megan was born, we were set on the fact the baby was going to be a boy. My whole family talked about it and my father knew we had decided to call him Joseph.
"But as it turned out, we had a girl and instead, I used the name Joseph for the character in my book."
Geoff, who lives at Blunts Wood, Haywards Heath, with wife Julia, Megan, and their youngest child Emily, ten months, said: "I have done lots of writing but this is my first success.
"It's very satisfying to see it in print, but I was really writing it for pleasure."
The process took nearly 16 months and was completed mainly on Geoff's homeward journey each evening.
The Lost Grandad is being launched on October 7, at Ottakar's bookshop, South Road, Haywards Heath.
It is also available at the Halcyon Bookshop, in the Broadway, Haywards Heath, and the Bookstop, in Lindfield.
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