The correct answer is B) It is surrounded on all sides by large bodies of water.
Why has mainland Britain MOST LIKELY not been conquered by outside invaders since 1066? Because it is surrounded on all sides by large bodies of water.
The last time Great Britain was invaded was in 1066. It was the Normans that sent their army to invade and capture the British island. Nevertheless, there are some historians that have documented that the Norman invasion was not the last one. It was a French invasion. Yes, the invasion of Fishguard in 1797, specifically in the southwest region of Wales.
Great Britain is surrounded by large bodies of water such as the Atlantic Ocean, which makes it difficult for enemies to enter the island.