July 1: So it begins. Don't worry, this is not in the correct legal jurisdiction!
Valve Stem Diameter
WARNING: This page is about a different car, the 2013 Land Rover LR4, 2012 Land Rover LR4, 2011 Land Rover LR4, and 2010 Land Rover LR4. However, it is still accessible from the selected car via links, so may be relevant.
Using a micrometer measure the diameter of the valve stems.
If the measurements are not to specification, install a new valve.