From the Thiepval Memorial and Visitor Centre return to the D151 and turn left before dropping down towards the Ancre Valley to Authuille.  In the village, double back to the left taking the small road east towards Ovillers which is signposted to Lonsdale Cemetery. As the road flattens out the back of the Thiepval Memorial can be seen to the northeast.  Immediately beyond the road was the Leipzig Salient.  About 1.5km beyond Authuille the road dips again into a valley close to the northern edge of Authuille Wood.  Where the track crosses the road after it has climbed again was the position known as The Nab.

The Nab was a sharp right angle in the trenches at the head of Nab Valley (later known as Blighty Valley) near the northeast corner of Authuille Wood.  To the south of the Nab ran the British front line and at one point it ran along what became known as Dead Man's Bank, only a few feet high and halfway across no man's land. It was the scene of many deaths on the first day of the Battle.

Among those attacking from here towards Pozières ridge on 1 July 1916 was Percy Boswell of the 8th Battalion, The King’s Own Yorkshire Light Infantry.  His unit, was positioned roughly mid-way between the Nab and Ovillers.  They were to advance over a long, gentle slope into strong German positions containing well-sited machine guns.  The first wave advanced under cover of British artillery, suffering relatively few casualties as they entered the German first line.  Behind them, however, over half of the second wave were cut down as they crossed the 320m of no man’s land.  All 25 officers, including Boswell, were either killed or wounded.

Confused fighting continued all day, until the British troops withdrew to their original trenches at the end of the afternoon.  The 8th King's Own Yorkshire Light Infantry suffered nearly 550 casualties – 80% of their attacking strength.  Percy Boswell has no known grave and is commemorated on the Thiepval Memorial.