Why did the british enter World War 1?

British policy for Europe was that no country be allowed to become too dominant. Close inspection made them conclude that the country with the biggest threat of dominance was Germany. It had a large population, a good economy and a huge army, fully capable of dominating Europe. Britain joined the Triple Entente with Russia and France. When Germany attacked France by going through Belgium, a country Britain had a treaty to protect, war was declared on Germany.