to be opened at on 1 July, as emplacements for batteries of Stokes mortars. The 252nd Tunnelling Company placed mine H3 north of First Avenue and Mary, beneath the German stronghold on the ridge. The miners had dug a gallery for about from the British lines about underground beneath Hawthorn Ridge Redoubt on the crest of the ridge and charged it with of Ammonal. The VIII Corps commander, Lieutenant-General Aylmer Hunter-Weston, wanted the mine to be sprung four hours before the offensive began so that the crater could be captured and consolidated in time for the alarm on the German side to have died down. On 15 June, the Fourth Army headquarters, ruled that all the mines on 1 July should be blown no later than eight minutes before zero; an unsatisfactory compromise was reached with Hunter-Weston to detonate the Hawthorn Redoubt mine ten minutes before zero hour. An earlier detonation of the H3 mine in the VIII Corps sector was expected to divert German attention to the north bank of the Ancre, which would help the attacks of X Corps and XV Corps further south, where success was more important. Opinion in the 29th Division was that time was needed for the débris from the great mine to fall to earth, although it was demonstrated that all but dust had returned to the ground within twenty seconds. Firing the mine early conformed to the plan to occupy the crater quickly but it required the heavy artillery bombardment of the redoubt and adjacent trenches to lift during the assault. All of the VIII Corps heavy artillery was ordered to lift at and the field artillery to lift at A light shrapnel barrage fired by the divisional field artillery was to continue on the front trench until zero hour; in the 29th Division sector, half of the guns were to lift three minutes early. British plan The 29th and 4th divisions were to advance east across the valley of Beaumont-Hamel to an intermediate line on Beaucourt spur and then advance to the second position in hours. British artillery fire would lift off the German front trench at zero hour and the field artillery was to move eastwards in six lifts, from the first objective after zero and then lift in succession after about twenty minutes on each of the further objectives, the heavy artillery lifting five minutes earlier each time. The