Query

I read recently that Florrie Cowley, a teleprinter operator at the Ministry
of Home Security, No: 5 (London) region control room says that she "sent
special mesages in groups of 5 letters without a single vowel"

I have lost the original reference so I don't know what period this was, but
maybe immediately post war.

This is probably something that is well known to afficionados but, pardoning
my ignorance, can anybody tell me what sort of code this might have been
please.

Ian Walker