While many tales of cunning and trickery have been associated with Twm, he is also said to have been a respected antiquary, genealogist and poet and to have risen to the position of magistrate and mayor of Brecon as well as being a relative of the occultist John Dee.

[4] It is considered unlikely however, that the numerous tales attributed to Twm Siôn Cati were the exploits of this one man but rather a number of raiders and highwaymen (possibly with similar or identical names to that of Thomas Jones) who operated in the Tregaron area.

As an illegitimate son, he unofficially took both his father and mother's names, becoming known as Thomas Jones in English, but as Twm Siôn Cati in common Welsh convention.

"Between eighteen and nineteen, in order to free himself and his mother from poverty which they had long endured, he adopted the profession of a thief, and soon became celebrated through the whole of Wales for the cleverness and adroitness which he exercised in his calling".

He was supposedly a Protestant by faith at a time when Mary I of England, a Catholic monarch, ruled and he had to gain an income as best he could, choosing robbery as his trade as his religion had him marked out as a rebel already and his low status meant that he could not rely on any advantage or protection from others.

In the tale told by Llewelyn Prichard, Twm woos and eventually marries the Lady of Ystrad-ffin and subsequently becomes a magistrate and mayor of Brecon.

The name of his first wife is unknown; his second, whom he married in 1607, was Joan, widow of Thomas Williams of Ystrad-ffin and daughter of Sir John Price of Brecon Priory (1502?-1555).

[8] A tale from Prichard's book involves an occasion when Twm is staying in an inn overnight and realises other people are planning to rob him the following day after he sets off.

Through this marriage Twm is supposed to have gained respectability, eventually becoming a justice of the peace, sitting in judgement on others, a position he held until his death aged 79.

There are a number of similarities between the legends of Twm Siôn Cati and the lead character of Henry Fielding' 1749 novel, The History of Tom Jones, a Foundling.

These include the circumstances of his birth, a noble father, a bucolic setting in the "far west", romantic liaisons followed by the meeting and wooing of a lady, exile from their home country, a rags-to-riches narrative structure and even the character's names (Thomas Jones).

Which was subtitled as "The jokester: a collection of feats and tricks of Thomas Jones of Tregaron, Cardiganshire, he who is generally known under the name Twm Sion Catti".

The journalist William Frederick Deacon dedicated a chapter of his 1823 work, The Innkeeper’s Album to "Twm John Catty: The Welch Rob Roy".

While the collection is of South Wales folklore, the chapter title was a clear attempt to copy Sir Walter Scott's success in repurposing the Scottish hero for nineteenth century British readers.

George Borrow, walking through Wild Wales in 1854, heard several tales about Twm from a fellow-walker on the way to Tregaron and later read what was probably Prichard's book.

This verse shows how much fear the local residents had of him: There is a great cheer and shout in Ystrad-ffin this year, And the snakestones melt into lead By the osom of Twm Siôn Cati.

Created by Lynn Hughes and starring John Ogwen as Twm and Jane Asher as Lady Johane Williams, the drama depicted Twm as a Welsh freedom fighter protecting Welsh people from the repression of the English Sheriff John Stedman (Jack May) and the cruel (Catholic) Vicar Davyd (Philip Madoc).

The Oxford Companion to the Literature of Wales notes that Prichard's vivid descriptions of Twm's cave suggest the author knew the area around Rhandir-mwyn well.

Historical accounts have been published by Lynne Hughes (whose book Hawkmoor, was serialised by the BBC in 1977) and three by Welsh-language children's author T. Llew Jones.