[2] In London, Robert Thomas either had a second marriage ("Lady Anne his wife" appears in birth records of the Parish of St. Giles in the Fields) or a mistress ("his own whore"[6]).
He finally sold his property in Glamorgan, Wales (Plas Llanmihangel, Bettws, Flemingston) to Humphrey Edwin for £12,812 in 1685.
[2] The last record of Sir Robert Thomas was on 29 Apr 1685 at the King's Bench Prison, when he signed a petition in support of Titus Oates, the notorious promoter of the Popish Plot.
[11] Though the circumstances of his death and burial are not known,[12][13] evidence from a court case[14] suggests that Sir Robert Thomas died before the end of 1685 (Old Style).
His Whig/anti-Catholic politics seem to have originated in resentment for the poor treatment his family received as Royalists during the English Civil War and Interregnum.
A third factor shaping his politics were friendships and alliances formed with prominent Whigs and anti-Catholics in Wales and in London, including John Arnold, Sir Trevor Williams, Ford, Lord Grey, and, later, Popish Plot conspirator Titus Oates.
[18] On top of these factors, Sir Robert's extremism was probably fueled by his dire financial condition in the 1670s and 1680s,[16][10] i.e. such political actions could be used against enemies and to curry favor with powerful friends.
In 1678-81 while a Member of Parliament, Sir Robert Thomas became embroiled in the anti-Catholic Popish Plot as an antagonist and accuser.
[3] Both in his home county of Glamorgan, Wales and in London, Sir Robert Thomas was a controversial person with a mixed reputation.
He was described variously as a "royalist sufferer",[17] "unmannerly behaviour" towards King Charles II and the Duke of York,[3] a "dubious ally",[16] a political "extremist" of the Country Party/Whig and anti-Catholic sort,[10] an "isolated adventurer"[10] rather than a Party loyalist, and a wealthy business person with "no sense".
Sir Robert was one of 25 friends attending the funeral of Samuel Butler at St. Paul's Covent Garden, and was a pallbearer along with Aubrey and Shadwell.
[19] Being a pallbearer is a notable act of friendship, in part because Butler "died in want"[19] (poverty) and was no longer a popular figure.
In 1671, his father Sir Edward Thomas, 1st Baronet, filed a petition with the House of Commons, complaining of "Miscarriages, Frauds and Abuses, committed by his said Son".
[20][21] In 1677, Sir Edward Mansel of Margam, also an MP, wrote private notes on the gentry of Glamorgan, and it included the following entry[6] (spelling in original, clarification in square brackets): In c.1684, a poem by an unknown author lampooning the gentry of Glamorgan included the following stanza with Sir Robert Thomas as subject[10] The lines "He never was good / To the next of his blood" apparently referred to the conflict he had with his father, mentioned above.