Special VFR in control zones

May be authorized by ATC for a VFR flight within a control zone when weather is below VMC minima.
Ground visibility at least 1500 m (800 m for helicopters); clear of cloud and in sight of the surface.
At night, normally limited to take-off/climb-out or approach/landing only, unless the competent authority permits otherwise.
Subject to ATC clearance and traffic conditions — it is not a right, only a possibility.

Source: SERA.5010 – Special VFR in control zones