Wealden Lake was a freshwater lake which existed over the lands now considered to be northern France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 and southern England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

 during the early Cretaceous

Cretaceous

The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 (around 140 million years ago). Alluvial plain

Alluvial plain

An alluvial plain is a relatively flat landform created by the deposition of sediment over a long period of time by one or more rivers coming from highland regions, from which alluvial soil forms...

s and deltas

River delta

A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...

 spread from the uplands surrounding the area where London

London

London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

 now stands and eventually ran into this great lake.

Global tectonic shift during the mid to late Cretaceous (especially in the Maastrichtian) raised, tilted and thereby drained Wealden Lake. It would have been around the size of the Caspian Sea

Caspian Sea

The Caspian Sea is the largest enclosed body of water on Earth by area, variously classed as the world's largest lake or a full-fledged sea. The sea has a surface area of and a volume of...

 at its best preserved extent during the early Cretaceous.

Strata associated with Wealden Lake have been prosperous for paeleontologists, providing the mysterious Baryonyx

Baryonyx

Baryonyx is a genus of carnivorous saurischian dinosaur first discovered in clay pits just south of Dorking, England, and later reported from fossils found in northern Spain and Portugal. It is known to contain only one species, Baryonyx walkeri...

dinosaur among many other finds.