It's the old staines and west Drayton line. Unfortunately it's closed due to gang violence between the West Drayton massive and the east staines upon Thames massive.
There is still a bit that goes straight through the m25/m4 junction ablietly single track but I'm sure it's been kept for a Heathrow connection at some point in the future. You can see it on Google earth.
https://youtu.be/uDP4Um4Nb7A
It's the old staines and west Drayton line. Unfortunately it's closed due to gang violence between the West Drayton massive and the east staines upon Thames massive.
There is still a bit that goes straight through the m25/m4 junction ablietly single track but I'm sure it's been kept for a Heathrow connection at some point in the future. You can see it on Google earth.