Dock bug,
Coreus marginatus.
A large and mottled reddish-brown squashbug with a broad, oval abdomen. The two small projections between the antennae are diagnostic. Picture shows two bugs mating on a dock leaf.
There is one generation per year, adults mating and laying eggs in spring. The nymphs feed predominantly on dock so you are likely to find them easily in the Wildlife Trail where dock is prolific. Photo Stephen Middleton