What about the other golden oldie that the Bakerloo Line *was*
secretly built as far as Camberwell Green in the late-40s?

One that *is* true is that the overrun tunnels at Charing Cross
Jubilee were built along the alignment of the Strand to allow for
future Fleet Line extension, plus to allow for the stabling of two
trains each, and reach just short of the Aldwych/Waterloo Bridge
junction.