Part 1

Probably the most famous example of banditry, as the fantasy RPGs would have it, would be to Coterel gang, active in Medieval England during the 14th century. James Coterel, the leader of the gang "is assumed to have been a younger son of Ralph Coterel, a landowner in Cromford, Matlock, Tadington, and three other places in Derbyshire". The Coterels got up to all sorts: "Between 1330 and 1332 James Coterel led a ring of gangs involved in murder, kidnapping, and extortion in the Peak District and northern Nottinghamshire."

The first recorded instance of the activities of the gang comes from 1328 when they, at the instigation of Robert Bernard, attacked the vicar of Bakewell and stole 10s from the Church offerings. What they did with the vicar's tarts is unknown. This indecent seems to have been vengeance for Bernard having been stripped of his position as vicar of Bakewell in 1327. Considering he was the kind of person who would resort to hiring a gang of criminals to do his dirty work, it is not hard to see why.

In 1329 we find John Coterel, another member of the gang, and associates raiding the estates of Henry, earl of Lancaster. The most interesting of these associates is Roger le Sauvage (Roger the Savage is an extremely good, extremely on the nose name for a bandit) who seems to have joined the operation due to his debts. Sauvage is interesting because he was the son and heir of John le Sauvage, who was the lord of Stainsby manor. This brings us to an important point which is that le Sauvage and the Coterels are well-to-do - they're the sons of wealthy land owners; "a century later such men would probably be classed as 'gentlemen'". This flies in the face of many of the tropes surrounding medieval bandits and outlaws you see in fiction, where it's very much presented as the preserve solely of the peasantry.

As a piece of trivia, the Coterel associates John and William Bradburne took part in a burglary in 1318 with one John 'the Little'.

The Coterels had achieved a level of infamy by around 1330. In this year they murdered John Matkynson and Sir William Knyveton. It also saw a serious attempt to bring them to justice, with James Coterel being forced to answer the charge of pillaging the earl of Lancaster's estates. The gang members don't appear to have gone along quietly, as it were, considering the sheriff had to postpone the proceedings four times, indicating that they were still at large. In response to this, the authorities appointed Sir Roger de Wennesley (who himself was guilty of several crimes, including the murder of Laurence Coterel) to bring them in. Bellamy suggests that he received this appointment because he was a sworn enemy of the Coterels. Wennesley failed (actually being persuaded to join the gang instead) and, as a result of their failure to appear, the Coterels were outlawed in 1331.

Following their outlawry from March 1331 to September 1332 they operated mainly in the Peak District and Nottinghamshire. James Coterel never stayed more than a month in one place and frequently returned to places where he was assured of a warm welcome, such as amongst the canons of Lichfield. As the jurors of Bakewell put it, the Coterels "rode armed publicly and secretly in manner of war by day and night." The size of James Coterel's gang in this period seems to have been at least twenty people, and possibly more. Of these recruits, most don't appear to have been criminals before joining up with Coterel. Coterel in this period seems to have been on top of a "federation of lesser units under his overall command rather than a monolithic structure". By the Autumn of 1331 the Coterels seem to have begun eschewing violence, it bringing more trouble than it was worth.

Bellamy argues that James Coterel was able to attract followers so easily because he made outlawry a very profitable business. Essentially they resorted to extortion through threats of violence. For example, James Coterel himself took 100s from Ralph Murimouth at Bakewell. A particular feature of the Coterel operation was the delivery of letters by a member of the gang demanding such and such a sum, to be paid to a representative of the gang, or their property would be burned. It was a pretty sophisticated, if nefarious, operation. These letters imitated the royal style, which Bellamy suggests was probably a deliberate parody. It was during this period that they aided the Folevilles in the kidnapping of Sir Richard de Willoughby. This kidnapping was probably at least in part motivated by vengeance; both the Coterels and the Folevilles had run afoul of Willoughby and his father on multiple occasions.

The Coterels continued to invite scrutiny in 1332 - the areas where they were active were visited by a commission of trailbaston which included the Chief Justice of Common Pleas and the Chief Justice of the King's Bench, indicating that they had earned the wrath of those in high places through their activities (though, they also enjoyed the favour of those in high places, see below). Once again though, the Coterels had little difficulty evading justice (receiving advance warning from multiple sources, including via their spies in Nottingham). Not all of their associates were so lucky - William de Uston, who had been an important part of their extortion operation, was sentenced to hanging (though the execution did not take place). 200 men were taken to appear before the King's Bench in connection with the Coterals and the Folevilles. There was a run of prosecutions from January to March 1333. However these proceedings were, it has to be said, a failure - even Uston ended up acquitted. There were a number of reasons for this, on the part of the juries, fear of reprisal, genuine sympathy, or worry about legal culpability if the men were found guilty and they in turn were suspected of knowing about, but not reporting, their activities.

By 1336 James Coterel is found in more legitimate pursuits, being entrusted by the Crown with administrative duties, including being charged with the arrest of a "miscreant Leicestershire parson". This is not to say that Coterel had given up his dastardly ways - in 1337 his was commissioned to lead sixty archers to Scotland. Coterel, naturally, absconded with their wages.

Robert Bernard, who instigated the first Coterel crime we have evidence of, was registrar of Lichfield Cathedral. Indeed the dean and canons of Lichfield were a major source of support for the Coterels, maintaining them at important points in their criminal career. They also received support from the canons of Lenton in the midlands. Indeed, friends in high places are very much a part of the Coterel story - members of the gang had ties to the party of Thomas, Earl of Lancaster (Nicholas Coterel being pardoned as one of his adherents) and James Coterel received the patronage of Queen Phillipa on multiple occasions (the Coterels were also tied to Queen Isabella through Ralph de Spayne). These were not political partisans though - whilst many members of the gang had strong ties to Thomas of Lancaster, others had ties to Edward II's supporters and none of them seem to have held Henry of Lancaster, Thomas' brother and heir in much regard. Another important link for the Coterels was their relationship with Sir Robert Ingram, who was "sometime mayor of Nottingham, sheriff of the Nottinghamshire and Derbyshire bailliwick and many times an M.P. for both county and borough". During their 1331-1332 period the Coterels also received the assitance of two other gang leaders, Sir William de Chechulton and Sir John de Leigh (more well-to-do criminals).

You asked if these people retired to a comfortable life somewhere. The answer, in the case of James Coterel is a resounding yes: "James Coterel repeatedly acted as tax collector for Lenton Priory in his later career, and was even entrusted with one arrest warrant in 1336 and another in 1350, when he and six others were instructed to find and capture three monks of Lenton who had left the priory, he still felt it necessary to obtain a pardon for extortions, oppressions, receivings of felons, usurpations, and ransoms in 1351."

John de Leigh (who ended up representing his county in parliament in 1322) and William de Chechulton, both mentioned above, surrendered at Nottingham Castle in 1332 and were employed to go after a pair of less competent criminals. This mirrors what we saw with Wennesley and indeed Coterel himself. The English judiciary in this period operated on a policy of using criminals to catch criminals. Many of Coterels former associates ended up taking part in military service. In general, by 1341 the appeal of criminality of the type that the Coterels were so successful at during the late 1320s and early 1330s seems to have lost its appeal. It was not, in fact, so uncommon, for these people to retire into respectability.

Active around the same time as, and tied to, the Coterels, was the Folville gang of Ashby Foleville in Leicestershire, who I've referenced through the first part of this answer (as Bellamy points out, the interlocking nature of the criminal gangs of this period is one of the most important points - there is an entire web of criminals active during this period, all of whom seem to have known each other, all of whom were, or were related to, land owners). Richard de Foleville was a priest; in 1340 when he took refuge in the church of Teigh he had been rector there for twenty years (his attempt to hide in the church ended with him being dragged out and beheaded). The Folville's, like the Coterels, were a gang of brothers, six of them in fact, one of which was the beheaded Richard.