"The Pals battalions, Kitchener's army, fought its first really major battle on the Somme.
"There is in Britain, to this day, a kind of particular link with the first of July 1916, because so many communities saw their young men cut down in this first huge, mass battle for the British on the Somme. The local newspapers in the following weeks were full of pages of pictures of local lads who laid down their lives on the Somme. I think the impact of these losses on particular communities has passed into the British collective folk memory. So the character of the British Army as a highly localized, distinct army of 1916, disappears with the Battle of the Somme.
"Haig's thoughts on the battle are still a subject of hot debate in Britain and in the rest of the historical world. The thing to remember is that it was a joint Anglo-French battle, and that the British took the bigger part in the battle. I think mainly because of the French involvement in Verdun.
"Originally, the whole object of attacking on the Somme is because this is where the French and British armies actually joined.
"Therefore, it's not Haig's choice of battlefield. Haig always preferred Flanders as his choice of battlefield in that sense.
"They used an early form of something called creeping barrage, which means you actually move your artillery fire in front of the troops so as to provide a curtain behind which the army will advance. They get the men into no-man's-land before zero hour, they're ahead of the game, and they win the race to the parapet.
"They've got the French artillery alongside them because this is where the army is actually joined. So they've got more firepower. And this combination of circumstances on the first day of the Somme means that on the right flank of the British line, things are done better, things are done properly.
"The first day of the Somme is remembered so much because it's the bloodiest day ever in British military history.
"Nearly 60,000 casualties, including nearly 20,000 dead. There was never an experience like this in the whole British military history, indeed British history. The Germans also lose heavily on the Somme, and the learning curve of the British Expeditionary Force and the Dominion Forces in the First World War, I think, really begins at this point.
"The ingredients are in place, nearly, by the middle of the Battle of the Somme. The problem is that the weapon system has a sort of unit that isn't yet properly balanced, in my view. There is not yet enough heavy artillery. The gunners do not yet know quite how to apply all their techniques to maximum benefit.
"The machine gun corps, which is being created, has not yet worked out its tactics properly. This is the first appearance of tanks during the Battle of the Somme – that needs to be shaken down, if you like, into a working tactical system. Cooperation with aircraft is not yet fully developed; and even the poor bloody infantry on the ground – the balance of their weapons isn't yet right.
"One of the things during the Battle of the Somme, is that you can get brave men to advance at any time.
"But it's sustaining the impetus of the advance once they've gone over the top that's important. If they've got the wrong weapons with which to fight, if they're carrying rifles and bayonets and they're up against machine guns, the formula is wrong.
"If, as is happening by the end of the Battle of Somme, and in 1917, you give them more light machine guns to carry into battle, and you give them more grenades, if you take more trench mortars forward with you – you give them more firepower. They're able to stick out there longer and sustain their own moment of advance. That's what I mean by balance of forces. Once you've got formula right, you can begin to work the tactics properly."