To follow on from this question a bit, I'd like to ask as to why we ever had secondmen in the first place if drivers were competent to operate alone? How did they justify this additional expense?
Secondmen were the follow on from the firemen. When diesel was brought in, I don't think the Drivers (or Unions) wanted to loose the presence of another chap in the cab as it was what they were used. Also, when you consider there were fewer safety systems in those days and more semaphore signaling, it was probably quite reassuring to have someone else alongside you, making sure you hadn't missed anything.
It's important to remember that secondmen were often the train drivers of the future. Instead of the long process of training that goes on now, drivers would have done much of their learning in the secondman grade, before undergoing a fairly short (by modern standards) classroom training process. From what I've read (I'm 21, so I can't speak from first had experience!
), you'd have to prove your reliability and suitability for the driving grade during your time as a secondman.
Also, they didn't have a hob on the other side of the cab for no reason. Who'd make the brew if the secondman wasn't there!
(Anyone feel free to correct what I've said, I'm only going on what I've read on the net.
)
EDIT: Doh, Bill gave a better answer quicker (Shouldn't be watching Top Gear and posting at the same time, slows me down :P ). Good to know I wasn't far off though.)