This case has the ingredients of a typical radiation fog: the fog formed within a slowly moving high-pressure ridge, in weak wind conditions. As the fog had formed, it persisted for days. This was due to weak solar radiation (December on 50th latitude) to erode the temperature inversion, lack of atmospheric fronts, which could have increased the surface wind and hence lift the fog. Within the high-pressure a general subsidence further enhanced the temperature inversion at the top of the boundary layer and maintained clear skies above the fog layer. Only when a new cloud layer approached the fog layer in South-east England, the radiative conditions were changed and the fog layer lifted off the ground.