Summary
The UK’s oldest satellite, Skynet-1A, launched in 1969, has mysteriously shifted from its original orbit over Africa to a high-risk position over the Americas.
It’s suspected that in the 1970s, Skynet-1A was intentionally moved west, possibly by U.S. controllers, but records confirming who made this decision and why are missing.
Now inactive, the satellite poses collision risks to active satellites, as it occupies a congested orbit at 105 degrees West longitude.
The UK may eventually need to consider relocating Skynet-1A or removing it altogether to mitigate risks from space debris.
No, it would have been detected by various systems pretty much immediately. Those systems are military though, and probably wouldn’t tell the general public about the movement of military satellites
It’s also conceivable that it was detected in that orbit but not recognised, so it was treated as a mystery object