Hitherto June 77, we had exchange SNCO's in the US system - the last 2 were Sgt Alan Mills and FS Pete Bree (acoustics operators). Some Senate members were never happy with non officer people working with military nuclear things. Allegedly the change was based on Hull no's. When the LA Class was introduced, Hull No (6**?) the exchange stopped due to a Senate motion - hence, NOFORN!
In truth, an aggressive US submarine quietening programme was introduced, and our lads had access to it, so they wanted them out
Pontious - Yes - USN exchange officers were not allowed on Cod War sorties in the event we had to emergency divert to Keflavik (a US Base) which might have caused a diplomatic incident! Ha!
In the mean time we were wired up for the NDB 550, but only if they said yes!