The Permian and Triassic
As the continent drifted northwards, away from the Equator, through the latitudes represented today by the Sahara desert, the erosion was renewed. This time, the lateritic soils are represented by the New Red Sandstone and the red soils of Leicestershire and Rutland.
The early Permian was the time of the height of the Variscan earth movements as the crust to the south was crushed against the island. The great disturbances seen at the surface in Brittany, the Ardennes and the Rhineland also lie below the Paris Basin. They fade out in the gentler anticline of the downs and Weald of southern England which overlies the edge of the island. The axis of this anticline is normally called the northern Variscan front. However, the chalk of the downs is Upper Cretaceous, so the process continued well after the Permian. The point in the present context is that the stability of the island contrasts with the relatively unstable crust to its south, which was forced into a long mountain ridge.
To the north, economically important things were happening. Western Britain was pushed up as part of the Variscan Orogeny while the east of Britain, including the island began to subside leaving a broad basin, north of the island and south of Scandinavia. This formed a shallow sea in a very dry climate. Desert sands and salt basins were a result but there are also mudstones. This provided the alternating porous and imperveous rocks which have trapped the gas escaping when the coal measures, below were subjected to geothermal heat. This has left a group of gas fields off the Norfolk coast. That is to say, off the coast of the island.
Read more about this topic: London-Brabant Massif