'Kay, I got it! It's not a clock symbol but a speedo symbol! I don't use cruise control so I must have inadvertently switched it on.
Thanks for the link, Ann! Much appreciated the manual is now tucked away on my PC!
David, I think the RT display is different to the F3 from what I can remember....colors and everything!
Chupaca.....errr...Thanks....I think!!

MBM....You're putting me to shame, mate! I've had my F3 longer than you've had your's and thus I should have known what it is.
My only excuse being that I have never used cruise so it's never appeared before! Wouldn't mind a copy of the WSM if you can see your way....