Richard II was still a teenager in 1386, remember, but there had never been a regency established (mainly because most people were deeply suspicious of John of Gaunt, the obvious guy for the job) and Richard had, nominally, ruled from the start. The reality was that at first the council took the strain, with the King gradually taking more responsibility as he grew older.
No sooner had Gaunt shot off to Spain to pursue his claim to the throne of Castile than the opposition, led by the King's youngest uncle, Gloucester, started to get stroppy. They imposed a one year Commission on Richard that was given power to supervise almost everything he did. Richard, unhappy with this, refused to co-operate and went off on progress, recruiting as many supporters as he could - mainly in Cheshire. He also put some questions to the judges about the legality of the Commission and the status of those who had advocated it. The judges were clear in their ruling - the Commission was illegal and those who had advocated it were traitors.
This ruling was kept secret, but walls at court had ears, and the news leaked out to Gloucester and his allies, who immediately had visions of their important heads being stuck on spikes. To cut a long story short Gloucester, with the earls of Warwick and Arundel, raised an army to defend themselves. They were joined by Henry Bolingbroke (Gaunt's heir) and Thomas Mowbray, the Earl Marshal, a little later. (These last two were young men, and Mowbray, previously in Richard's in-crowd, had lately married Arundel's daughter.)
Robert de Vere, Duke of Ireland and Earl of Oxford, tried to bring a royalist army down from Cheshire, but was defeated at Radcot Bridge in Oxfordshire, and had to flee the country. King Richard, stuck in the Tower and virtually defenceless, had no choice but to grant the demand of the Appellants (as the rebels are known to history) for a parliament and the trial of their enemies.
The Appellants proceeded to rub Richard's nose in it just has hard as they dared. They conducted a purge of his household, excluding various people they thought a bad influence, and used the Parliament to treat various of Richard's advisers as traitors. Most of those they could get their hands on were executed, while the judges who had given Richard such dangerous advice were banished to Ireland for life. Needless to say, the Appellants concluded business by arranging for themselves to be voted a healthy bonus for their trouble! The tone of the Parliament has come down to us in its name - The Merciless Parliament. It was exactly that.
If you read the Chronicles of the time you may gain the impression that Richard had ignored the advice of his elders and listened to the young, thus bringing about this disaster. This is pure unmitigated weapons-grade BS, worthy of Dr Goebbels. There was only one of those accused by Parliament who was remotely young - Robert de Vere, a man in his late twenties and holder of one of the premier earldoms in the country. Sir Simon Burley, for example, had been a trusted servant of the Black Prince and Richard's tutor. Michael de la Pole, Earl of Suffolk had served Gaunt for donkey's years before taking office under Richard. You don't need me to tell you that the mayor of London and the senior judges of the land were scarcely to be described as boys!
No, what these people had in common was that Gloucester and his friends regarded them as being in the way, or, in the case of the judges, dangerous to their health.
Some of this might have been justified had the Appellants proved themselves better at government than Richard who, it must be admitted, had not exactly been setting the house on fire with his ability. The fact is they were no more up to the job than he was, and arguably less so. Richard's people skills soon detached Bolingbroke and Mowbray from the coalition, and in 1389 the King simply announced to his council that was taking power back into his own hands. No one said a word to the contrary.
Richard immediately began to build up a new party of his own supporters - one of the leading lights in this was his cousin, Edward of York, Earl of Rutland. Moreover, as soon as Gaunt returned to England, Richard offered him a new deal. The political landscape was dramatically transformed.