wrote:

Aidan Stanger wrote about his idea for major engineering work in the
Willesden Jn area...


It would be done one track at a time. Apart from
rebuilding Willesden Junction station, all it needs
is a bit of diversion S of Willesden Junction so
that the tunnel can surface between the tracks, and
a new flyover at the N end. Temporary flat junctions
could be installed to enable these to be constructed.

[SNIP] probably a weekend or two of rail replacement
buses on Bakerloo and Silverlink S of Watford
Junction, and the trains might take slightly longer
for a while. Virgin Trains wouldn't be disrupted.

You seem very optimistic. But since most major civil engineering
projects end up taking far longer than predicted, I can't share your
optimisim! This would probably end up taking months just for
"rebuilding Willesden Junction station" alone -- never mind diverting
the tracks, putting up flyovers etc.

I never said it wouldn't. The couple of weekend posessions would be to
install flat junctions, and a bit of third rail electrification so that
the trains can run on tracks other than those they'd normally use in
Willesden. This they'd do for months (probably taking a few minutes
longer than normal) while they rebuild the station and put up flyovers
etc.