This is a very good example of a curiously shaped flint nodule. Flints have all come out of the soft limestone formation of the Upper Chalk. The Chalk was formed in a sea which covered most of Northern and Central Europe and Britain during the Late Cretaceous period just before the extinction of the dinosaurs (and much other life) in the end Cretaceous extinction. All flint, including your specimens, is 85 to 65 million years old.
Flint nodules are formed by an accumulation of silica gel from the brakdown of the skeletons of siliceous sponges on the ancient sea floor.This specimen is probably a trace fossil, as tooth, claw and other odd shaped flint nodules usually formed when the silica gel flowed into burrows left by animals such as crustaceans (shrimp-like animals with a hard external skeleton) on the sea bed and later hardened.
I've attached a bit more information about how flint forms.