Borbus
If I am interpreting the documents correctly, this way appears to have finally been opened and is now Emberton Public Bridleway 20: https://www.milton-keynes.gov.uk/consultations/625

This follows the landowners trying to close the other public bridleways (18 and 19) in 2016 which appears to have been unsuccessful.

A survey is needed to establish the way is physically open and confirm with the council maybe that the PRoW now exists.