Britain lacks the railway geography for a hidden mobile deterrent

Could HS2 or another British railway support a rail-mobile nuclear deterrent?

Britain has very little suitable railway geography: missile trains would need long, remote routes with enough traffic to conceal them without overwhelming the timetable.

A rail-mobile deterrent needs long routes with enough ordinary traffic to conceal special trains without crowding the timetable. A very busy high-speed line is too constrained, while a nearly empty route makes every movement conspicuous. The desired route would also pass through sparsely populated areas for long distances. That combination describes very little of Britain's railway geography.