Man with the rosette

An individual described in historical records as simply "the man with the rosette" or "the man with the blue-and-white rosette" (PROSE: The Adventuress of Henrietta Street) was one of the four surviving elementals who survived the destruction of Gallifrey. (PROSE: The Gallifrey Chronicles, The Adventuress of Henrietta Street)

Origins
The man with the rosette and the Doctor had been rivals who knew each other very well before the post-War universe. They had many duels with "all of time and space as [their] battlefield", with the Doctor frequently stopping the man from causing great disaster. This bond was so intense that the amnesiac Eighth Doctor briefly recognized the man, exclaiming "good grief" in a manner reminiscent of a prior Doctor the man had frequently fought: (PROSE: The Adventuress of Henrietta Street) the Third Doctor, close rival to. (TV: The Dæmons, Day of the Daleks, The Curse of Peladon, The Sea Devils, The Time Monster, The Three Doctors, Frontier in Space, et al.)

The man's prior identity as the Master was also hinted at the Doctor's remark that he used to have a "terrible beard". (PROSE: The Adventuress of Henrietta Street) One account indicated that the man's future self remembered this entrapment within Lolita's sister and being freed from it when his people needed him, (WC: Overture to 'Sabbath and the King') mirroring how became trapped inside the Doctor's TARDIS after fighting the Eighth Doctor in San Francisco (PROSE: Sometime Never..., The Gallifrey Chronicles, TV: Doctor Who) only to be eventually drawn out by the Time Lords so he could participate in the Last Great Time War. (PROSE: Doctor Who and the Time War)

Alternatively, while bearded, the man with the rosette looked identical to the Magistrate within the Infinity Doctor's reality. (PROSE: The Gallifrey Chronicles, The Infinity Doctors) Some accounts indicate the Magistrate lived prior to the War in Heaven, (PROSE: The Infinity Doctors, The Ancestor Cell) and his last known moments were when Omega used God-like power to vanish the Magistrate somewhere "out of harm's way". (PROSE: The Infinity Doctors) Two of the other four surviving elementals also resembled contemporaries of the Magistrate who had left Gallifrey immediately after the Omega event, suggesting that this vanishment was how the Magistrate survived to become the man with the rosette. (PROSE: The Gallifrey Chronicles, The Infinity Doctors)

According to the Primer for the Spiral Politic, some believed that the "Rosette-wearing man" was the War King after his mysterious disappearance from the Homeworld. (AUDIO: Sabbath and the King)

Attending the Doctor's wedding
The man travelled to Earth in the 18th century and sat with Scarlette in a pub during a brawl. He wore a blue-and-white Whig rosette and spoke with her about politics. He left before the Eighth Doctor arrived.

He later met Scarlette at the London docks, where he gave her a pair of rings for the Doctor's wedding. At the Doctor's wedding he sat in the seat reserved for the Doctor's family. He did not interact with the other guests but simply sat quietly and helped himself to the wine.

The man left a wedding present for Scarlette: a fake rose of blue and white satin, resembling no flower on Earth.

The man later met the Doctor in the Kingdom of Beasts. As they stood on a hill, they talked about the state of the universe without Gallifrey in it. The man told the Doctor that he would not fight him because there were only four of their kind left in existence. He told the Doctor that Sabbath and his people were now the future of the universe before he quietly left.

The man was present at the fall of the house on Henrietta Street, where he told Lisa-Beth that he was leaving and that, if he couldn't find something to alleviate his boredom, he would go to sleep until the universe was ready for him again, even if it took a million years. He then walked away from the house on Henrietta Street. (PROSE: The Adventuress of Henrietta Street)

Alleged subsequent solitary activity
The historical document detailing the Doctor and Scarlette's wedding gave the above as a final note on the man with the rosette. The so-called "individuals claiming to be the Doctor" were modern appearances of the Doctor which the historian took as imposters due to the impossibility of a human surviving so long and/or changing physical appearance, suggesting the black-clad man the historian thought they recognised as a resurgence of the man with the rosette (PROSE: The Adventuress of Henrietta Street) may have actually been pre-War incarnations of the Master in their face-offs against earlier incarnations of the Doctor, such as the Third, throughout the 20th century. (TV: Terror of the Autons, The Dæmons, etc.)

In the Imperial Family
In a vision of the four surviving elementals, the Eighth Doctor and Marnal saw the man wearing his blue rosette. (PROSE: The Gallifrey Chronicles)

The four elementals joined together to found the Imperial Family of the Needle, (COMIC: Miranda) propagating their species and renewing Gallifreyan rule over the universe for a while with the Doctor as their Emperor. (PROSE: Father Time) While the man with the rosette had derisively told the Doctor that he wasn't interested in joining in on the Doctor becoming "King of Time", (PROSE: The Adventuress of Henrietta Street) another source indicates he was the Emperor's "Magistrate".

A loa once showed a vision of the Magistrate absently toying with his rosette while waiting with the Imperial Ministers on the Throneworld for the end of the Emperor's century-long exile. (PROSE: The Story So Far...) The Doctor's century on Earth occurred before the Doctor's wedding in the Doctor's timeline, (PROSE: Father Time, The Adventuress of Henrietta Street) but the wedding seemed in the Magistrate's past given that he still wore the rosette in response to it. (PROSE: The Adventuress of Henrietta Street, The Story So Far...)

The Imperial reign lasted for 1000 years, growing decadent and cruel in its final centuries before ending in a Klade revolt. While many of the Family were killed on the Needle, some fled into the depths of the past, intersecting with the Eighth Doctor's century on Earth. Zevron believed that he had tracked every single one of these survivors down and killed them with a special ceremonial knife. (PROSE: Father Time)

Fate
Being a member of the Imperial Family, the man was believed to have been killed. (PROSE: Father Time, The Story So Far..., COMIC: Miranda)

The Primer for the Spiral Politic, a publication controlled by the Imperial Family during their rule, (PROSE: A Prelude to a Prelude) indicated that most scholars believed the Rosette-wearing man went on to become the War King. (AUDIO: Sabbath and the King) The War King, who came to his homeworld before the War in Heaven with knowledge of the coming conflict, (PROSE: The Book of the War) once said that he had "travelled so far" to become King. (WC: Overture to 'Sabbath and the King') He also recalled having the titles "Magistrate" and "Minister", (AUDIO: Sabbath and the King) both of which were associated with the Imperial Family. (PROSE: The Story So Far...)

Appearance
The man with the rosette had jet-black hair that greyed at the temples, which he kept slicked neatly back with oil. (PROSE: The Slow Empire) He had a sallow face. While the Eighth Doctor had a beard, the man was cleanshaven; (PROSE: The Adventuress of Henrietta Street) after the Doctor shaved, the man grew a pointed black beard. (PROSE: The Gallifrey Chronicles)

He spoke with an English accent and was of "distinguished middle age." Considered handsome in some respects, he was noted to be slim, of average height, and had "well manicured hands." (PROSE: The Adventuress of Henrietta Street)

Consistently well-dressed, he always wore tight, prim, black outfits. Pinned upon his lapel was a blue and white rosette, which signified the colours of the Whig party. (PROSE: The Adventuress of Henrietta Street)

Personality
The man with the rosette was quite gracious and civil, though he could come across as 'swarthy and difficult to place'. Now being one of only four survivors of the destruction of Gallifrey, he found that he must "offer the universe" whatever the Doctor did not.

Undisturbed by violence, the man with the rosette longed for the days where he could duel the Doctor across the whole of space time and hoped that the universe would one day be ready for their game to begin once more. Despite this, he believed that such games would be inappropriate in a universe where Sabbath and "his kind" were in charge. He seemed to enjoy being mysterious about his true identity, simply bowing his head to those who asked about him. (PROSE: The Adventuress of Henrietta Street)

Behind the scenes

 * In Lance Parkin's AHistory, Parkin acknowledges that creator Lawrence Miles intended the man with the blue-and-white rosette to be the Master. His use of the character in the unlicensed short story The School of Doom (published in Myth Makers #12), which tied in with his novel Father Time, was even more explicit on this point.
 * The dedication of The Dark Path implied that who became trapped inside the Doctor's TARDIS was a duplicate grown by the Tzun in First Frontier, having created more than one genetically-engineered "resurrection" of  in the course of their experiments. This provides a potential avenue for the man with the rosette to be a contemporary Master to the Eighth Doctor despite not being trapped inside the TARDIS.
 * Also in AHistory, Parkin acknowledged a "fan consensus" that The Infinity Doctors was set on a reconstructed Gallifrey following The Gallifrey Chronicles, though he simultaneously noted that this was not his intention at the time. If taken seriously, this notion might lead to the conclusion that the Magistrate of The Infinity Doctors, interpreted as the Magistrate of a post-Gallifrey Chronicles, restored Gallifrey, might be the man with the rosette's eventual future self with no time travel involved. This is distinct from the suggestions in other sources that the man with the rosette travelled back in time to before the War to become the War King, though some sources place the Magistrate in the War King's past rather than in a post-War era of the universe.