If 50 pounds you can afford...

...go ahead and pull the cord.
If 50 pounds you do not own
Leave the bloody thing alone.

Clearly someone on my train home a few days back had £50 to spare, although I imagine the fine is somewhat larger now than it was back when the communication cord was an actual cord hanging down from the vicinity of the ceiling. Our train came to a screeching halt somewhere outside Woking, which was later explained by the guard as being because someone had pulled the emergency lever in one of the carriages. We sat for quite a while and then carried on to the next station we were going to stop at anyway at which point the guard then had to go through all the carriages to find out which one it was - odd that they didn't already know. Fortunately that was my stop anyway, so I wasn't too late and annoyingly, it meant I didn't get to find out what had happened either.

Shame.