The woman opposite unzipped her bag and dragged out a giant cured sausage. Then she found a knife and started hacking off slices. She offered me one.

“No, gracias,” I said.

I was on a train crawling through the night between Madrid and Murcia, in south-east Spain. At the brave age of 20 I decided it would be more interesting to fly into the Spanish capital to begin my year studying abroad, rather than the nearer, much more convenient airport.

So I travelled in one of those trains where you sat in compartments, trying to avoid eye contact or, worse, foot contact with those opposite.

Pretending I understood their tic-tic-tic Spanish.

It was dark, I was lonely, and I was far from home.

When the train arrived at 6am I was in a new world. What I noticed most, as I negotiated with a be-cardiganed taxi driver, was how Spain smelled different: sticky-sweetness mixed with drains mixed with coffee.

That was the scent of home for the next year.

I’ve become attuned to the smells of home in the decades since. Foggy diesel on a London winter night, sheep poo and bracken on Lakeland hills, mud and shellfish on the frayed Suffolk coast.

Perhaps home is more than our four walls and a postal code. Maybe instead it’s about the environment: the cuisine, the blossom and the detritus that make up where we live.

Is it possible that home is what gets up our nose and under our skin?