Lords' Strong, Casewell and Beesbury could not believe their luck when they heard from Lord Jason Lannister what Queen Alicent had yelled out before a crowd of people outside the Great Sept in King's Landing. Hundreds of people heard what she said so there was no way to deny it. When nobles like Jason Lannister, who were not part of the conspiracy, were turning their backs on the Hightowers, they knew it was time to act. It was time for those who acted against the crown to pay for their crimes.
So they gathered the other members of the Small Council except for the King, Ser Otto and Grand Maester Mellos and Lord Strong shared with them the evidence collected more than 20 years previous by the, then, Princess Rhaenyra. The three also shared the written accounts of Lord Corlys and Princess Rhaenys of the events that transpired while the Royal couple had been abroad in Mercia, particularly how Queen Alicent tried to kill Rhaenyra and her family by setting their home ablaze (and how unrepentant Queen Alicent had been about how her actions that night may have led to the deaths of many other people who lived in the same village as Rhaenyra). Their account also told how Alicent had taken a dagger and had tried to stab Rhaenyra but how Rhaenyra had been able to block it but still wound up with a long cut down her arm. The accounts further spoke of how Alicent herself had confessed so much before them and the people of the village but how King Viserys had chosen to defend his wife.
When the other Councilors had finished going over everything, they were appalled. This could not be let stand. Queen Alicent had attempted murder under the "orders" of Ser Otto. They had arranged the ruin of the young heir to the throne which had led to her disinheritance. Since Queen Alicent had also not managed to even birth a single child, and now, as everyone knew was permanently unable to do so, it rendered the realm unstable as the Crown literally had no heirs.
In the accounts by both Corlys and Rhaenys, they spoke of how Rhaenyra had no intention of ever returning to Westeros as she loved her life and freedom in her new homeland too much nor could she imagine asking her husband to abandon his Lord to move to a place that had so completely rejected her. She also refused to subject any of her children to the ways and culture of Westeros especially since they would be seen as being lesser since their father was a bastard despite all of Rhaenyra's own children being legitimate offspring.
The King's next closest possible heir was his brother, Prince Daemon who had been exiled more than 20 years previous and, outside of short visits to High Tide, had not been seen in Westeros since. In the years since King Viserys had disinherited and banished his daughter, he had tried many times to convince Daemon to return to Westeros and to his court to no avail. Daemon had settled beyond the Black Walls of Volantis with his dragon and seemed to be extremely content there. Daemon had written multiple times that there was no way that he would ever be willing to take up the heirship again nor that he would ever want to be King of Westeros as he dubbed it a viper infested cesspit.
It was well known that Prince Daemon had taken Lady Laena Velaryon to wife and that the pair had children together. Despite many letters written by King Viserys begging to know the names and genders of Prince Daemon's children, neither he nor his children's grandparents would reveal the information. What had been known is that both Prince Daemon and Lady Laena had written that they and their children did not consider themselves part of the Targaryen of Westeros family tree nor the Royal line of succession.
Yes, there was still Princess Rhaenys but her daughter had excluded herself from the succession along with her children and Princess Rhaenys' son had no intention of marrying or begetting children of his own which meant that line was a dead end for heirs as well.
Vaegon the dragonless, while he was still alive, had made it very clear at the Great Council that he had no interest in the throne leaving the only other Targaryen as Sarera but her father had ruled that neither she nor any of her descendants could ever sit the throne.
Viserys literally had no heirs and the ones that had the smallest claim were far distant cousins in the Baratheons.
Getting back to the matter at hand, the council decided to act. They quickly called for the arrest of Grand Maester Mellos, Ser Otto and Queen Alicent and had them taken to the Black Cells where Lord Strong promised that his sons would ensure that all three were ready to talk in a moon's time, which would give as many Lords and Ladies of the realm time to arrive at the Red Keep for the grand trial, including those from the North and the Vale who usually were not at court unless summoned.
That very day messages were sent out throughout all of the kingdoms, including Dorne.
That moon was extremely busy for the Councilors as they collected further evidence against the traitors.
As for the King, when he found out that all the Lords and Ladies of the realm had been summoned, he was positively delighted and quickly sent out his own missives ordering them to bring all of their unmarried daughters aged ten and above with them. Yes, he was aware that his wife had been stabbed, that she had actually not gotten pregnant despite his best efforts and that even before the trip to Mercia, he probably should have set her aside as she was barren even then, but it really didn't matter much to him. Soon he would have the best pick of the sweetest maidens in the realm and would have new Queens in his court as well as beautiful mistresses dancing around. He also did not notice the absence of Ser Otto in his daily life or that Otto, Alicent and Mellos had been arrested by his council. All he could think of was the beautiful brides he soon would have.
The day of the trial finally arrived. The council had informed the King of what was going to happen along with all of the evidence that had been gathered and he just told them to do whatever they thought was best as he trusted them. The King chose to wear his finest apparel to the trial so that he could spark interest in the young wives and young maidens in attendance that day knowing that during the course of the proceedings, he would be seeking out which ones he intended to bed first. Perhaps he would even take a few to bed immediately after the boring issues of court were done? Yes, he would love having several little flowers in his bed at a time to indulge in and so that is exactly what he would do. He just hoped that they would not grow jealous of one another as he had plenty of seed for them all and he truly did plan to wed as many of the maidens as who caught his eye.
Before the prisoners were brought in, the Council presented before the court all of the evidence. They shared the long time conspiracy against the crown and how it had crippled the crown as there had been no heirs in 21 years.
After the evidence was shared, Mellos was brought in. It took very little prompting for him to answer every question asked of him by both the Council and the Court. He was quickly found guilty and sentenced to be gutted like he had done to Good, Sweet Queen Aemma. After he was dead, his head was to be hung from the front gates of the Red Keep.
Otto was next and he could not stop blaming his daughter for everything. If she had not failed her duties. If she had kept her mouth shut. If she had managed to actually kill Rhaenyra and her family and so much more vitriol was spewed from his mouth. However, despite everything he said, it was very quickly apparent to all that were gathered that he was indeed guilty. He was sentenced to death by being drawn and quartered and then hung. Once dead, his head would also be removed and hung from the front gates as well.
Finally it was Queen Alicent's turn.
"My King! My Love! Please! Save me!" she begged but Viserys remained silent as he eyed the 13 year old twin daughters of Lord Redwyne, 11 year old daughter of Lord Rosby, 16 year old daughter of Lord Redfort and her twin, the 16 year old wife of Lord Brax, 18 year old wife of Lord Peake and 14 year old wife of Lord Fell. Viserys immediately decided that once he could leave, he would take the Redwyne twins with him. He'd never taken twins so it was going to be fun. He did wonder what it would be like when he took the other twins since one had already been wed and bedded and the other was still a maiden.
Even through her eyeless sight, Alicent kept crying and begging Viserys for his aid as the Council and court interrogated her. However, he did nothing until the very end.
"Your Grace," asked Lord Strong, "do you wish to say anything before a sentence is delivered to your wife?"
Viserys then stood, "Alicent Hightower has been a curse to me. In one and twenty years she has only managed to have her womb quicken four times and not once has she managed to carry to term. My dear Aemma, Gods' rest her, carried eight babes to term, seven of whom died in the cradle and birthed another six near or full term stillborn babes so fourteen total and that's not counting the numerous miscarriages she had in between each. I need heirs and despite endless promises, Alicent has failed to deliver. I say its time for her to lose her head."
Alicent gasped at the King's words. "NO! Viserys, I'm your wife!"
"You destroyed my daughter and only living child to the point where she refuses to interact with me and have been an endless failure. Gods willing that your replacements will do what you've failed to do. Guards! Take her to the block. I want her head off within the next half hour!"
So Alicent Hightower was dragged out to the block while Viserys approached the Redwyne twins with the intent to convince them to come into his chambers with him unaccompanied by anyone other than the other.
Over the next few months, more members of the conspiracy were rounded up, tried and executed. As for Viserys, well, let's say that a few girls and women he ordered executed when they refused his advances but all of the others that he wanted, he took and this kept him busy enough that he left his Council to run everything for him.