Here's one from an FHM.com visitor who signed my guestbook over the weekend:
"Apparently one year at Christmas a tube driver decided to have some fun, stopped the train in the middle of a tunnel, and said in a deep voice, "This is your driver speaking...(pause)...or is it?" What a man! "
What a psycho!
Update - just in case you don't read the comments (shame on you)
Looks like this driver (Redd Pepper), or someone like him has now got a job as a voiceover artist. LordofMisrule gives us the full story.