The word ‘nobility’ is a vague term; no society in history could be described as having an upper social tier whose members were all of equal wealth and statues. The Anglo-Saxon aristocracy certainly had more than one stratum, and any detailed study of these men must entail a definition of these different levels.
In the eighth-century, Bede wrote of a group of men called ‘comites’, the Anglo-Saxon translation of which is ‘gesiths’. In origin, a gesith was an honourable companion, usually of the king. Most often he would be of noble birth, and he would be either a retainer or the holder of an estate. By the tenth-century, the word was no longer used to describe a personal retainer. HR Loyn  suggests that by this time the gesith may well have been a retired retainer settled on his estate. He suggests further that the pattern in the tenth-century may have been as follows:
“The retainer at court was termed ‘thegn’. If he was promoted , he became an ealdorman, and when he retired he became a ‘gesith’.”
Whatever the truth of the matter, it is clear that by the tenth-century the thegns were subordinate to the king’s thegns and to the ealdormen, and that the gesith was no longer engaged in active service for the king.
One distinction between the gesith and the thegn was that of age; the thegn was a young man, the gesith more mature. Initially the thegn was not a powerful man, the term sometimes merely denoting a servant, albeit one who was free. By the tenth-century, however, ‘thegn’ had taken on a more specialised meaning. The law codes of the period show us something of how the thegns had become more important as servants of the king. They were given the responsibility of helping the king to ensure that the church was observing its rules:
And I and my thegns shall compel our priests to that which the pastors of our souls direct us (clerical celibacy).” 
It is also clear that the thegns now had their own class, with a recognisable rank:
“And my thegns are to have their dignity in my time as they had in my father’s.” 
Anglo-Saxon society was not a static one. Thegnship had developed as a class of its own, but this did not mean that one had to be born into that class to belong to it.
“And if a ceorl prospered, that he possessed fully five hides of land of his own, a bell and a castle-gate, a seat and a special office in the king’s hall, then was he henceforth entitled to the rights of a thegn.” 
It is doubtful how many achieved this, but the opportunity was at least there in theory.
Thegns were graded according to their relationship with the king. The king’s thegns would recognise no other lord than the king  and might themselves be lords to other thegns. The lesser thegns would have a lord other than the king. Their heriot (see below) would go to their lord, not the king.
From among his thegns the king appointed ealdormen. These men were the king’s representatives in the localities. The main ealdordoms were Northumbria , East Anglia, Mercia and Wessex. The office was not strictly hereditary, although many ealdormen succeeded their fathers. In the king’s lands his presence was felt through his reeves, but increasingly the king’s reeves were used as a check against the ealdormen. A grant of King Aethelred II’s shows that an ealdorman had no authority to deal with a breach of law by a king’s reeve, and had to appeal directly to the king. 
The Witan was the high council, and its members were powerful wealthy thegns, and bishops and abbots. The bishops were powerful men, usually from noble families themselves. The witness lists to royal charters show a strict order of seniority. The king signs first, followed by the archbishops, bishops and abbots. The ealdormen sign next, followed by the king’s thegns. Among the ealdormen, there was also a strict order; the most influential of the moment signed above the others. Usually the order changed following the death of an ealdorman, but it was possible for some to gain prominence without such an event. Eadric Streona, Ealdorman of Mercia in the reign of Aethelred II, headed the lists in the lifetime of men who had at one time been his seniors.
The heriot (war-gear), as defined in II Cnut  also demonstrated seniority of rank: among the earl’s heriot is the requirement “eight horses, four saddled and four unsaddled.” The requirement of the king’s thegn is “four horses, two saddled and two unsaddled.” Of the lesser thegn the corresponding requirement is for “a horse and its trappings.”
The law of the North People, and the Law of the Mercians  show the position of the nobility in relation to lesser men. The Law of the North People sets out the wergild* thus:
The wergild of the archbishop and the atheling is 15,000 thrymsas
That of a bishop and an ealdorman 8,000 thrymsas
That of a king’s high-reeve 4,000 thrymsas
That of a mass-thegn and a secular thegn 2,000 thrymsas
A ceorl’s (churl) wergild is 266 thrymsas
(* wergild was essentially the price, or worth, of a man’s life; a payment due to the family by the person who killed him)
In the Law of the Mercians a ceorl’s wergild is 200 shillings, and a thegn’s wergild is “six times as much.” So between the thegn and the atheling, the wergild is doubled each time. In contrast, the thegn’s wergild is six times that of a ceorl. Despite the professed opportunity for social mobility, the Anglo-Saxon aristocracy was clearly set apart from the rest of society by a substantial distance.
As well as possessing considerable rights over his lands and his vassals, a lord had a duty to safe-guard his men. The terms of the fealty oath are vague, but there is other evidence which describes more fully the nature of the personal bond between a man and his lord. In the reign of Edward the elder (899-924), a letter was written to the king describing the history of an estate at Fonthill, Wiltshire.  It describes how a thief, Helmstan, was required to give an oath to clear himself of the charges brought against him. He asked his lord Ordlaf to intercede for him, which Ordlaf did, even though his man was guilty. Although this practice was forbidden  there are many other illustrations in the law codes of the lord’s obligations to his man.
A tenant who did not pay his rent could expect his lord to be lenient and exact no penalty.  If an accused man ran away, his lord had the responsibility of paying the man’s wergild to the king.  Any master who forced his slave to work on a feast day forfeited the slave and paid a fine.  An accused man could expect his lord to stand surety for him, and if the man ran away from the ordeal it was the lord who had to pay his wergild. 
The betrayal of a lord was beyond compensation, according to the laws of Cnut.  The personal bond was a two-way responsibility, and the man must be seen to honour his obligations to his lord. The Battle of Maldon shows how seriously this responsibility was taken. Eadric resolves to serve his lord in battle and “now that the time had come to fight, before his lord he duly kept his vow (hold-oath).” When Byrhtnoth is killed, his men have a duty to avenge his death. Traditionally this means that they have to kill the whole of the Viking army to ensure that they kill the actual soldier by whose hands Byrhtnoth has been slain:
“They all intended one of two results,
To love their lives or to avenge their dear one.”
In this stratified society, every man had a duty to protect the men in his care, and to serve the man who protected him. At the top level, the king of course served no-one, and had only the responsibility of protecting his people. At the lowest levels of society the obligation would be only service. The aristocracy had two duties: they served the king (and their lord if they had one) and in return they were rewarded. They had their own men who served them as lord, and in return they offered their man protection, especially under the law.
 Gesiths and Thegns in Anglo-Saxon England from the Seventh to the Tenth century – HR Loyn
 IV Edgar 1.8.
 IV Edgar 2.a.
 EHD (English Historical Documents) Vol 1 52 – A Compilation on Status (1002-1023)
 “And no-one is to have any jurisdiction over a king’s thegn except the king himself.” III Aethelred 11
 Because of the Scandinavian influence in the north, the ealdormen in Northumbria were termed ‘Eorl’
 EHD 117 page 525
 EHD 50 page 419
 EHD 52 – A Compilation on Status
 EHD 102 page 501
 II Cnut 20.1 “Many an over-bearing man will, if he can and may, defend his man which ever way it seems to him that he can defend him more easily … but we will not allow that abuse.”
 II&III Edgar 1.1.
 II Cnut 31.1.
 II Cnut 45.3.
 III Aethelred 4. & 6.2.
 II Cnut 64.
This article first appeared on the EHFA Blog on April 26th, 2016