The Road Vehicles (Construction and Use) Regulations 1986
http://www.legislation.gov.uk/uksi/1986/1078/regulation/107/made
AS SUGGESTED BY
https://www.gov.uk/government/uploa.../file/401565/pathway-driverless-cars-main.pdf
quote:-
There is nothing explicit in law to say that a vehicle cannot be driven
by someone not in the driver seat. Regulation 104 and 107 of the
Construction and Use Regulations are pertinent here. These are
discussed in more detail in Chapter 10. They require a driver to be
positioned where they can control the vehicle and have a full view of
the road, and not to leave the engine running while the vehicle is
unattended. It would arguably be possible for a driver outside the
vehicle to be in a position both to control it and see the road ahead of
the vehicle but, depending on the precise circumstances, the view
requirement might not be met. It is not clear how a court may interpret
the requirement for a vehicle to be “attended” when a “remotely
positioned driver” is controlling it, but it is arguable that a person does
not have to be sitting in a vehicle in order to “attend” it
Which would indicate to me that UK legislation has yet to catch up with the "remote parking pilot" on the public highway. How legislation might apply on private land might be different.