In May 1536 the marriage of [her husband] Thomas Howard (age 25) and Margaret Douglas Countess Lennox (age 20) was discovered by [her uncle] King Henry VIII (age 44). She, Margaret Douglas Countess Lennox (age 20) was next in line of the succession at the time of the discovery. Henry promptly enacted retrospective legislation and imprisoned both Thomas and Margaret in the Tower of London [Map]. Thomas was attainted and remained in the Tower of London [Map] until his death a year later.

Hall's Chronicle 1536. Around Jun 1536. In the Parliament season Lord [her husband] Thomas Howard (age 25) without the King’s assent affianced the Lady Margarete Douglas (age 20) daughter to the [her mother] Queen of Scottes (age 46)Margaret Tudor Queen Scotland (age 46) and near to the King (age 44) for which presumptuous act he was attainted of treason, and an Act made for like offenders, and so he died in the Tower [Map], and she was long there as a prisoner.

18 Jul 1536. Attainder of Lord Thomas Howard 1536 28 Hen 8 c24 by which [her husband] Thomas Howard (age 25) was attainted for having married the [her uncle] King's (age 45) niece Margaret Douglas Countess Lennox (age 20) in secret thereby attempting to "interrupt ympedyte and lett the seid Succession of the Crowne" (she, Margaret Douglas Countess Lennox (age 20), was heir to the throne at the time). The Act sentenced Howard to death although it wasn't implemented.

On 29 Oct 1537 Margaret Douglas Countess Lennox (age 22) was released from Syon Abbey [Map].

Wriothesley's Chronicle 1537. 31 Oct 1537. This yeare, on All Hallowe Even, the Lord [her husband] Thomas Howarde (age 26), brother to the [her brother-in-law] Duke of Northfolke (age 64), died in prison in the Tower of London, and his bodie was caried to Thetforde, and there buried.

Allso the Ladie Margarett Duglas (age 22), that had lyen in prison in the Tower of London for love betwene him and her, was pardoned by the King and sett agayne at her libertie; howbeit, she tooke his death very heavilie.¹

Note 1. In 1644 she married [her future husband] Matthew fourth Earl of Lennox (age 21), and became Conntess of Lennox, and mother of [her son] Darnley.

Wriothesley's Chronicle 1551. 04 Nov 1551. The 4 of November the sayd Quene (age 35) rode from the sayd place to the Kinges pallace at Whitehall by Westminster in hir charyot, accompanyed with diuers knightes and gentlemen, carles and lordes, the Lady Margaret Dowglas (age 36), the Duches of Richmond (age 32), the Duches of Suffolke (age 32), the Duches of Northumberland (age 42), with diuers other noble women of England and ladyes of Scotland followinge after them; the Dukes of Northumberland (age 47) and Suffolke and the Lord Treasurer (age 68) receivinge her within the Court gate, all the guard standinge on euery syde of the Court; and at her entringe in at the hall the Kinges Maiestie (age 14) stode in the upper ende of the hall, the Earle of Warwicke (age 24) [Note. assumed to be referring to the subsiduary title of the Duke of Northumberland] houldinge the sworde afore the Kinge; she kneelinge downe, the Kinges Maiestie tooke her up and, kissinge her, he tooke her by the hand, she comminge with him, he led her up into the chamber of presence, and so from thence to the Queues chamber of presence, where he kissed all the ladyes of Scotland, and so departed for a while; and that daye she dyned on the Quenes syde with the Kinges Maiestie, the Kinges service and hers comminge both togeather, richely serued in gylt plate; the Kinges seruice on the right hand of the table, and the Quenes on the left hand, she sittinge by the Kinge apart by his cloth of estate; the goodly cupbord of plate of gould and gylte that day there occupyed, with the rich hanginges and costly meates, was wondrous to see. All the ladyes of England and Scotland dyned in the Quenes great chamber, and were serued in siluer all theyr meates; dinner ended, the Kinges Maiestie shewed her his galleries and gardens, with other commodityes of that place; and about foure of the clocke he brought her downe againe by the hand into the hall, where he received her and there kissed hir, and so she departed to the Bishops house againe to Pawles in lyke manner as she went thither.