Ian,
Thanks for that explanation. It was much as I thought. As a humble NSA Met Airman in the mid 1950’s (and infesting some of the less glamourous overseas Staging Posts) I well remember the panic upstairs in ATC when the a/c call-sign “IRIS” was heard over the r/t (for those of you who don’t know IRIS was the a/c call-sign of the RAF Inspectorate of Radio Services – the ATC policemen/trappers)
Tks
Resmoroh