Chris Rogers > Or perhaps it was actually propelled by a 91,
>> bewitched to look like a normal carriage, and headed up by an ECML
>> DVT, bewitched to look like a steam engine!!!
>
> I reckon that she used Floo powder to travel from a brazier in the
> Guard's compartment to the firebox.....
Yes, of course, that's it!
Now, about the Knight Bus.... The book description doesn't sound anything like a triple-decker RT.