Dammit, we took out the model train set to play with today, but we couldn't make it go. After about half an hour, between shining the contacts with steel wool, tweaking the connector cables between the contact unit and the power unit, and messing with the loco, we got it to work.
However our floor is not 100% level and this caused a lot of problems. We couldn't get carriages to attach to the loco for any length of time for example. This was probably just as well due to sustained feline interest in the moving thingie.
Luckily there were no fatalities although the driver (DH) was quite amused.
In future though we have to find some way of levelling the ground under the track - the dining table isn't wide enough as the layout is roughly square. I mean, James May managed this outdoors for 4 miles, so it can't be that hard. We did get a paper layout backing thing with the set but it's spectacularly ugly....
(Yes, I put the set away carefully afterwards. DH says, remember to put your toys away when you have finished playing with them!)