Who was the leader of the british army in the battle of the somme?

{| ! ! ! ! | Combatants and casualties sufferred were: Great Britain 360,000+ Canada 24,029 Australia 23,000 New Zealand 7,408 Ireland 25,000 South Africa 3,000+ Newfoundland 2,000+ Total British Empire 419,654 French 204,253 Total Allied 623,907 Germany 465,000 |}