From
The MirrorSmoked mackerel and boiled eggs top list of foods - never to eat on a train
Over half of passengers always bring a snack with them for train travel - but 87% go out of their way to avoid those travelling with smelly foods
Smoked mackerel, boiled eggs, curry, and egg sandwiches are among the top food that should never be eaten – when travelling on a train, according to research.
Over half of Brits (55%) who have travelled by rail in the last year have prepared food to take with them, with 45% admitting they always pack a full picnic spread for longer journeys.
[snip]
Some even admit to bringing along a sushi platter for the trip, and one respondent always packs prosecco and posh picnic bites when heading for Royal Ascot.
Personally, I used to love that Katsu Chircken takeaway on the concourse at King's Cross - ideal to buy a carry-on meal before joining the Cambridge Express.