A watching brief on a trench being dug by Northumbrian Water in Throckley yielded further important evidence. The trench ran for 2.2 km along the berm, parallel to wall, giving a long, but very narrow, glimpse of the post pits, and proving they extend as far as Throckley. In addition, it also produced a most important piece of evidence; as the pits approached the position of Turret 11b on the wall, they changed direction towards it. What is significant here, is that the ditch does the same thing, curving to towards the turret. This suggests that the post pits, ditch, and turrets are part of the same system, at least at this point. It has puzzled archaeologist why the ditch curved in towards the turrets creating a narrowing of the berm, a phenomenon observed in several places, , but this is explained if the rampart represented by the post pits ran between, but in front of, the turrets, along with the ditch, as a temporary expedient, while the stretches of stone walling linking the turrets on a more direct line were under construction.
Historical sources: Engineering the battlefield
There is quite a detailed account of the building of these works, which is worth reproducing in full:
LXXII. Caesar, on learning these proceedings from the deserters and captives, adopted the following system of fortification; he dug a trench twenty feet deep, with perpendicular sides, in such a manner that the base of this trench should extend so far as the edges were apart at the top. He raised all his other works at a distance of four hundred feet from that ditch; [he did] that with this intention, lest (since he necessarily embraced so extensive an area, and the whole works could not be easily surrounded by a line of soldiers) a large number of the enemy should suddenly, or by night, sally against the fortifications; or lest they should by day cast weapons against our men while occupied with the works. Having left this interval, he drew two trenches fifteen feet broad, and of the same depth; the innermost of them, being in low and level ground, he filled with water conveyed from the river. Behind these he raised a rampart and wall twelve feet high: to this he added a parapet and battlements, with large stakes cut like stags' horns, projecting from the junction of the parapet and battlements, to prevent the enemy from scaling it, and surrounded the entire work with turrets, which were eighty feet distant from one another.
LXXIII.--It was necessary, at one and the same time, to procure timber [for the rampart], lay in supplies of corn, and raise also extensive fortifications, and the available troops were in consequence of this reduced in number, since they used to advance to some distance from the camp, and sometimes the Gauls endeavoured to attack our works, and to make a sally from the town by several gates and in great force. On which Caesar thought that further additions should be made to these works, in order that the fortifications might be defensible by a small number of soldiers.
Having, therefore, cut down the trunks of trees or very thick branches, and having stripped their tops of the bark, and sharpened them into a point, he drew a continued trench everywhere five feet deep.
These stakes being sunk into this trench, and fastened firmly at the bottom, to prevent the possibility of their being torn up, had their branches only projecting from the ground. There were five rows in connection with, and intersecting each other; and whoever entered within them were likely to impale themselves on very sharp stakes. The soldiers called these cippi.
Before these, which were arranged in oblique rows in the form of a quincunx, pits three feet deep were dug, which gradually diminished in depth to the bottom. In these pits tapering stakes, of the thickness of a man's thigh, sharpened at the top and hardened in the fire, were sunk in such a manner as to project from the ground not more than four inches; at the same time for the purpose of giving them strength and stability, they were each filled with trampled clay to the height of one foot from the bottom: the rest of the pit was covered over with osiers and twigs, to conceal the deceit.
Eight rows of this kind were dug, and were three feet distant from each other They called this a lily from its resemblance to that flower.
Stakes a foot long, with iron hooks attached to them, were entirely sunk in the ground before these, and were planted in every place at small intervals; these they called spurs.
The one of whom, being more secure from danger by their height, might throw their darts with more daring and to a greater distance; the other, which was nearer the enemy, being stationed on the rampart, would be protected by their galleries from darts falling on their heads. At the entrance he erected gates and turrets of a considerable height.
18. Flamininus . . . . ordered all his soldiers to cut stakes for a palisade to carry with them for use when required. This appears to be impossible when the Greek usage is followed, but on the Roman system it is easy to cut them. For the Greeks have difficulty in holding only their pikes when on the march and in supporting the fatigue caused by their weight, but the Romans, hanging their long shields from their shoulders by leather straps and only holding their javelins in their hands, can manage to carry the stakes besides.
For the Greek stakes, when planted round the camp, are in the first place easily pulled up; since when the portion of a stake that holds fast closely pressed by the earth is only one, and the offshoots from it are many and large, and when two or three men catch hold of the same stake by its lateral branches, it is easily pulled up.
Upon this an entrance is at once created owing to its size, and the ones next to it are loosened, because in such a palisade the stakes are intertwined and criss-crossed in few places.
With the Romans it is the reverse; for in planting them they so intertwine them that it is not easy to see to which of the branches, the lower ends of which are driven into the ground, the lateral prongs belong, nor to which prongs the branches belong. So, as these prongs are close together and adhere to each other, and as their points are carefully sharpened, it is not easy to pass one's hand through and grasp the stake, nor if one does get hold of it, is it easy to pull it up, as in the first place the power of resistance derived from the earth by all the portions open to attack is almost absolute, and next because a man who pulls at one prong is obliged to lift up numerous other stakes which give simultaneously under the strain owing to the way they are intertwined, and it is not at all probable that two or three men will get hold of the same stake.
But if by main force a man succeeds in pulling up one or two, the gap is scarcely observable. Therefore, as the advantages of this kind of palisade are very great, the stakes being easy to find and easy to carry and the whole being more secure and more durable when constructed, it is evident that if any Roman military contrivance is worthy of our imitation and adoption this one certainly is, in my own humble opinion at least.
Recruits are to be instructed in the manner of entrenching camps, there being no part of discipline so necessary and useful as this. For in a camp, well chosen and entrenched, the troops both day and night lie secure within their works, even though in view of the enemy. It seems to resemble a fortified city which they can build for their safety wherever they please. But this valuable art is now entirely lost, for it is long since any of our camps have been fortified either with trenches or palisades. By this neglect our forces have been often surprised by day and night by the enemy's cavalry and suffered very severe losses. The importance of this custom appears not only from the danger to which troops are perpetually exposed who encamp without such precautions, but from the distressful situation of an army that, after receiving a check in the field, finds itself without retreat and consequently at the mercy of the enemy. A camp, especially in the neighbourhood of an enemy, must be chosen with great care. Its situation should be strong by nature, and there should be plenty of wood, forage and water. If the army is to continue in it any considerable time, attention must be had to the security of the place. ……………………………………… ………………………………………There are two methods of entrenching a camp. When the danger is not imminent, they carry a slight ditch round the whole circuit, only nine feet broad and seven deep. With the turf taken from this they make a kind of wall or breastwork three feet high on the inner side of the ditch. But where there is reason to be apprehensive of attempts of the enemy, the camp must be surrounded with a regular ditch twelve feet broad and nine feet deep perpendicular from the surface of the ground. A parapet is then raised on the side next the camp, of the height of four feet, with hurdles and fascines properly covered and secured by the earth taken out of the ditch. From these dimensions the interior height of the entrenchment will be found to be thirteen feet, and the breadth of the ditch twelve. On the top of the whole are planted strong palisades which the soldiers carry constantly with them for this purpose. A sufficient number of spades, pickaxes, wicker baskets and tools of all kinds are to be provided for these works.
There is no difficulty in carrying on the fortifications of a camp when no enemy is in sight. But if the enemy is near, all the cavalry and half the infantry are to be drawn up in order of battle to cover the rest of the troops at work on the entrenchments and be ready to receive the enemy if they offer to attack. The centuries are employed by turns on the work and are regularly called to the relief by a crier till the whole is completed. It is then inspected and measured by the centurions, who punish such as have been indolent or negligent. This is a very important point in the discipline of young soldiers, who when properly trained to it will be able in an emergency to fortify their camp with skill and expedition.
"The Praefect of the camp, though inferior in rank..., had a post of no small importance. The position of the camp, the direction of the entrenchments, the inspection of the tents or huts of the soldiers and the baggage were comprehended in his province. His authority extended over the sick, and the physicians who had the care of them; and he regulated the expenses relative thereto. He had the charge of providing carriages, bathorses and the proper tools for sawing and cutting wood, digging trenches, raising parapets, sinking wells and bringing water into the camp. He likewise had the care of furnishing the troops with wood and straw, as well as the rams, onagri, balistae and all the other engines of war under his direction. This post was always conferred on an officer of great skill, experience and long service, and who consequently was capable of instructing others in those branches of the profession in which he had distinguished himself."
The legion had a train of joiners, masons, carpenters, smiths, painters, and workmen of every kind for the construction of barracks in the winter-camps and for making or repairing the wooden towers, arms, carriages and the various sorts of machines and engines for the attack or defence of places. They had also travelling workshops in which they made shields, cuirasses, helmets, bows, arrows, javelins and offensive and defensive arms of all kinds. The ancients made it their chief care to have every thing for the service of the army within the camp. They even had a body of miners who, by working under ground and piercing the foundations of walls, according to the practice of the Beffi, penetrated into the body of a place. All these were under the direction of the officer called the prefect of the workmen.
Timber Wall theoretical models
- Form the foundations of the wall;
- Hold the horizontal components in position;
- Support the fighting platforms.
- Two sets of posts allows for two fighting platforms at different heights.
- Thick end at the back, thin end pointed to the front;
- Made from standard lengths of timber 10 –12’;
- Stubs of branches help interlock the baulk.
- At an angle 60° to axis, [Bracing];
- Running across the structure [90° to axis];
- Parallel to the axis behind or in font the lines of posts.
- Simple design;
- Standard components;
- Simple to fabricate;
- Flexible, offering multiple configurations;
- Very strong interlocked and braced structure;
- Difficult to penetrate;
- Individual components difficult to remove;
- Can be dismantled and reused.
There are a series of ditches and gullies, crossing the site roughly N-S, but about 85° to the line of the wall, the spacing of these gullies about 90-100’ [pes] apart with a central pair about 40’ apart, together with some areas of possible surfacing, is suggestive of a Roman road crossing the site. This being the case, then the road would have lead to the facilities on the riverbank prior to the construction of the wall, running north along the east side of Wallsend Golf Course, where its line may have been preserved in the landscape.
- The size range of the trees.
- The density of trees in the woodland.
- The proportion of woodland in the countryside.
The Ditch and the Temporary Wall
The postholes, which have been found as a result of area excavations and watching briefs under the urban sprawl of Tyneside are the only physical evidence for the Timber Wall. Its presence elsewhere can only be inferred from the width of ‘the berm’, the space between the Wall and Ditch. 
The presence of the timber wall explains not only why the berm is so wide, but also why most of the ditch spoil was thrown to the north, with just a small amount to the south. Placing the spoil in a wide low bank to the north has little strategic advantage. In this context would appear that it is being ‘disposed of’ rather than being ‘used’. However, in the context of a temporary Wall, soon to be replaced with a stone one, the distribution of spoil and the width of the berm make sense. We might also expect that the long-term plan would be to widen the Ditch, once the Wall was completed.
Dislocation and The temporary Wall