You may have had to have the 2391 twenty years ago,but the Niceic long ago ditched that requirement
To satisfy the entry criteria,a QS has to demonstrate skill in test and inspection only
They will accept the 2391 or the new 2392, if you hold neither,this is their requirement
For those Qualified Supervisors who are able to demonstrate their ability to inspect, test, verify, certify and report on the electrical
installations to the standard required, the requirement to have obtained the City & Guilds 2391 may be waived