The rules on when bikes are classed as legitimate luggage seem to be in a bit of a spin

Could the passenger who has left a folding bicycle in carriage D please make themselves known as the bicycle is being removed from the train as it is causing a blockage!

This excited request came over the PA system this week on a severely overcrowded InterCity train I was travelling on, after some passengers had got off at one of the stops.

Although the bike was folded, and smaller than many of the suitcases blocking doorways all along the train, I watched (in impotent commuter-sheep mode) as it was duly ejected, and two police officers were called when the owner asked for a second opinion.

"The bicycle was illegal, it was causing a blockage," the train manager announced to the multitude when the train finally moved off again.

As discussed previously on this blog, cycling provision on trains varies around the country, and according to the time of day. The same varying provision for bikes affects trams too.

The official line of First Great Western, whose service this was, is that "Cycles are welcome on our trains ... we encourage the use of folding bikes which can be easily taken on board trains." The company says non-folding bikes can be refused if the dedicated spaces for them are taken – in the guard's van on an InterCity. But "folding cycles can be carried without charge on any service at any time". Which is good.

But in the cut-and-thrust of a crowded train, it can be slightly different. Train staff don't stop people boarding when all seats are taken, and I've yet to see someone being asked to move a suitcase away from an exit. But folding bikes seem to tweak the nose of power. They need to behave. Any trouble and they're out.

In the days when I used to take an Airnimal folder on my commute, it needed to be very neatly stowed in the luggage rack to avoid the attentions of some staff, who suspected it of being an ordinary bike trying to trick its way into the train.

It raised an interesting ontological question. How long does a bike's edgy, authority-challenging bikeyness survive? Is it still essentially a bike after it's folded? According to the incident I witnessed this week, it is. What if it hasn't got its wheels attached? What if it's in a suitcase? Completely dismantled? Or melted down?