Roger Mortimer and his uncle Roger Mortimer of Chirk were imprisoned in the Tower of London in February 1322 after taking part in the unsuccessful Contrariant rebellion against Edward II and the Despensers. The two men surrendered to Edward at Shrewsbury in January 1322, supposedly, according to some chroniclers, after the earl of Pembroke and other earls loyal to the king lied to them and promised them that the king would grant them a pardon if they did so. Well, maybe, but they would have had to have been pretty gullible and naive to think that they'd be offered a pardon after committing so many crimes: armed rebellion against the king, destroying lands and homes all over England and Wales in May 1321, forcing Edward to banish the two Hugh Despensers, destroying much of Gloucestershire when the king advanced on them in early 1322, and taking part in other Contrariant crimes such as homicide, assault, theft, false imprisonment and extortion. I'm pretty sure Roger Mortimer wasn't that naive, and given that forces led by Edward II's ally Sir Gruffydd Llwyd had captured their castles and that the rebellion was collapsing around them, I don't really see what other choice they had but to surrender.
On 14 July 1322, five men – the mayor of London, three justices of the court of Common Pleas and the chief baron of the exchequer – were ordered to try the two Roger Mortimers, and on 2 August condemned them to be drawn for their treason and hanged for their arson, robberies, homicides and felonies. Edward II had on 22 July, however, already commuted their sentence to life imprisonment, which would prove to be one of the worst mistakes he ever made and seems to defy explanation, unless he was remembering the Mortimer family's long service to himself and his family.  I looked recently at the possibility that Edward II, despite his decision of the previous year to spare the younger Mortimer's life, was planning to execute him in 1323, and that this is the reason why Mortimer escaped. It's possible, but is a story which appears in some chronicles but not others and is not corroborated by any evidence in the chancery rolls or other government sources. Roger Mortimer of Chirk died still imprisoned in the Tower of London on 3 August 1326, aged about seventy. Roger Mortimer of Wigmore, future self-appointed earl of March and favourite of the queen, escaped from the Tower on 1 August 1323, and here's what we know about the event.
With Roger Mortimer on the continent beyond his reach, Edward II lashed out vindictively at his family. This was no doubt inspired at least in part by his frustration at being unable to re-capture his enemy, though as Mortimer had sent assassins to kill Edward's friends, it is hardly surprising that the king would retaliate, and Mortimer chose to flee the country in the full knowledge that he was leaving his family to Edward's not-so-tender mercies. I n March and April 1324, his wife Joan and her servants were moved from Southampton to Skipton-in-Craven, and three of their eight daughters – Margaret Berkeley, Joan and Isabella – were sent to separate convents and granted the pitifully small amounts of fifteen pence (Margaret) or twelve pence (Joan and Isabella) per week for their sustenance.  As far as I know, three of Mortimer's four sons also remained under guard, though Geoffrey was reunited with his father on the continent, about which much more in the second part of this post, soon.
1) Calendar of Patent Rolls 1321-1324, p. 249; Ibid. 1327-1330, pp. 141-143. The judgement on the Mortimers is printed, in the original French, in James Conway Davies, The Baronial Opposition to Edward II (1918), p. 565 (...pur les Tresons soiez treynez et pur les arsons roberies homicides et felonies soiez penduz).
2) Calendar of Close Rolls 1323-1327, p. 13.
2) Ibid., p. 132.
3) Patent Rolls 1321-1324, p. 335.
4) Close Rolls 1323-1327, pp. 133, 137-138, 140-141.
5) Patent Rolls 1321-1324, p. 349.
6) Close Rolls 1323-1327, pp. 87-88, 106.