Terry Baker came across this article –
A retired Boeing 747-200 with mock US presidential transport markings has been barged up the Potomac River for an Air Force One Experience at Maryland's National Harbor Center.
Delivered to Singapore Airlines in 1973, it was last employed by Evergreen International Airlines five years ago.
(Source: Flight-International October 15, 2018)
And this photo from the same magazine dated October 23, 2018.
How close is close! This photo of a BA 747 on the normal flight path while landing from the west at LHR, probably over Colnbrook.