Separating two arrivals north and south runway
Another question has been submitted on this topic.
In IMC or using radar separation only, Director (FAD) is permitted to reduce separation to a 2.5nm stagger between the two runways and wake turbulence separation is not a factor.
If there were catch-up and the 2.5nm were to be infringed, the radar separation can be replaced with visual separation (ICAO term: reduced separation in the vicinity of the airfield). This can be applied by the aircrew involved, by calling visual with the traffic ahead or by the tower monitoring both runway finals when VMC exists.