If you hold an ICAO ATPL with +500 hours multi crew, you have to do a type rating or if you have +500 hours on that type, a check ride with a CAA examiner. The check ride more or less encompasses an initial IR.
If you hold an ICAO CPL or ATPL but don't have 500 hours multi crew, tough, you need to do a 55 hour multi IR course. (you get - 5 hours off).
Blame JAR.
