Originally Posted by Fuji Abound
Assuming you dont have an IR or IMC its only value is enabling you to transit a class A CTR such as Heathrow and fly at night (assuming you have a night rating).
In both instances flight is not permitted under VFR, so for example a low level transit of Heathrow can only be given under a SVFR clearance.
If you have an IR or IMC it enables you to continue to fly in visibility which would not meet the criteria for VFR but avoids you having to declare IFR.
The above is wrong in so many ways it should be ignored completely.
SVFR is only available in CAS that extends to the ground (CTR or zone)
Most typically used to cut corners off the Heathrow (Class A) zone to the west of that zone and to get into the CIs when you don't have an IR.
Also used at any airport inside CAS at night by anyone without an IMC (upto class D) or IR [as well as a NR/NQ of course
].
The only viz reduction is in relation to accepting an SVFR clearance, and that viz reduction enables the holder of an IMC or IR to accept viz of 3000m (3km) instead of 10000m (10km).