Why give the Special Operations Executive its own organisation?

Why establish SOE separately instead of running its work through MI5 or MI6?

A separate organisation could limit the damage to other intelligence activities if its personnel or operations were compromised.

A question about using MI5 or MI6 instead leads to an explanation of organisational separation. A distinct Special Operations Executive could carry out its work without exposing every other intelligence activity if it were penetrated. Compartmentalisation is the central justification offered. The answer also connects the early discussion with plans for personnel to remain behind after a German invasion and disrupt the occupiers.