In message , at 11:01:59 on Fri,
23 Feb 2007, Andrew Clark
remarked:

No-one knows where most of the Royals are anyway.

In normal times it's published well in advance.

hijacking a train and seizing exclusive use of part of the network for
the necessary time.

But if mass panic has hit London, the Tube network will not be running
anyway.

Indeed. It will have been closed for normal traffic for some time. Which
is why it's easily available for various (not just Royal Family) special
operations.
--
Roland Perry