Rover P6 gets a much needed lift EP16 2024 

Some cars had the reserve tap under the fuel tank and others had the tap at the rear of the engine compartment. Your tap may have been "adjusted" to incorporate the electric fuel pump. For what it's worth, it's far better to have the option of an electric pump that is fitted at the rear rather than the easy fix of installation in the engine bay where fuel vaporization problems may not be completely cured because engine temperatures. It will be interesting to see what condition the rear calipers are in. They certainly don't like periods of inactivity as my own P6B restoration project has proved. Interesting design though, if you get to stripping them down.

That old n plate must have been from a time when people were doing okay loads of n's from this part of the 70s