Charles Ellson ) gurgled happily, sounding
much like they were saying :

The Met is certainly a tube line.

It is not. It is entirely surface (or subsurface in some places),
but never tube. That line is run entirely by A stock, which is
surface stock, and would not fit in tube tunnels.

Even if you consider the Metropolitan to include the Circle,H+C,ELL,
it still isn't tube.

sigh
Tube in the sense of "London Underground", rather than tube in the
sense of the actual engineering behind the line itself.

"Tube" in the sense of a buzz-word slavishly copied without bothering
to recognise the correct meaning ?

Yes, that'll be it.

Otherwise known as "in the sense that several million Londoners use it
every day, rather than the sense that a handful of railway anoraks insist
on it being used when they're feeling *really* pedantic and trying to score
points..."