You will notice that the far side is higher than where you are standing. This probably indicates that that is the back of the trench. Soldiers on watch would have stood on a ledge above the bottom of the side nearest you, so that they could see the enemy.
This would have made them partly visible to the enemy and vulnerable, so the bank behind, being higher, would help to make them less easily seen by preventing a silhouette.
The ground where you are standing slopes gently away from the edge of the trench and forms a protective barrier to incoming fire. This is known as a parapet. The rear, higher bank is called a parados.
The cuts in the far side are L-shaped and may have been used by off-duty soldiers for resting. Here they are about 10 metres apart and are probably closer than they would have been on the Western Front, as the different groups of soldiers coming to Billericay would have needed training in actually digging as well as using trenches.