NATS have diddly squat to do with the terminology.
The Chicago Convention on International Civil Aviation lays down the framework that signatory States (including the UK) undertake to comply with. NATS is simply the contractor that the CAA uses to fulfil its obligations under the Convention.
The actual terminology is laid down in ICAO Standards and Recommended Practises (SARPS).
Kolibear - thanks - I did draft some of the text.
The idea came from Sam Spurdens, Marketing Manager at Archant, publishers of Pilot, with financial support from the sponsors and UK AIS.
Sam has recently gained his PPL.
