You may recall that Thomas Mowbray, Duke of Norfolk, and Henry (Bolingbroke) of Lancaster, Duke of Hereford had at least one thing in common. They had sided with the Appellants against Richard II in 1387/88 and with Richard II against the other former Appellants in 1397. They were issued with nice new pardons to go with their fancy new titles, but both must have been aware that they were not exactly flavour of the month with the King.
One day in December 1397, near Brentford on the outskirts of London, Henry Bolingbroke was riding along the road, quietly minding his own business. Along came Mowbray, who took him aside, and told him of a massive conspiracy that was going to ruin them both.
This is according to Bolingbroke, and, annoyingly, we only have his side of the story. As usual with historians, when there is only one side to a story available they tend to accept it as being true. I put it to you, Dear Reader, there is a possibility that it could all be a steaming pile of BS.
Anyway, according to Mowbray (according to Bolingbroke) the King was still out to get them for the events of 1386-88. Moreover, there was a court conspiracy to dig up the judgement on Thomas of Lancaster (Edward II's reign, please refer to the excellent Alianore blog for detail) and use it to forfeit the Lancastrian inheritance. The Duke of Surrey (Thomas Holland the King's youngish nephew) and the earls of Wiltshire (Scrope) and Salisbury (John Montagu) had drawn the Earl of Gloucester (Thomas Despenser, York's son-in-law) into a plot to destroy Gaunt and, while they were at it, take out Aumale (Edward of York) Exeter (John Holland, the King's half-brother) and Worcester (Thomas Percy). These last three, plus Norfolk, had taken an oath to resist this. Oh, and the King was trying to bring March into the plot too.
If there was truth behind all this, it would have made the night of the long knives look like a Sunday picnic! What it perhaps does demonstrate was that there were a lot a frayed nerves out there, and that men were looking for friends and fearing potential enemies.
It is true that there was a degree of hostility to and jealousy of John of Gaunt. This was nothing new, it had being going on for almost the whole reign. Something particular was developing in early 1398 because Sir William Bagot was bound over in the sum of £1000, which he would have to forfeit to the King if he was shown to have brought about the disinheritance of Lancaster or his family. A couple of days later he submitted to be executed without further process if he were to kill or put to death Gaunt or any of his family! (If you're interested you can find these amazing documents in the Calendar of Close Rolls 1396-7 pp 291-2). It's worth mentioning that although Bagot was at this point a favoured servant of the King, it was not that much earlier that he had been a retainer of Lancaster.
It seems likely that someone, maybe even the King, was behind Bagot's apparent plotting. However, it does beg the famous question posed by Charles II to his brother. Who would kill me, to have you? King Richard had achieved a modus vivendi with Gaunt. Why on earth would he want to get rid of Gaunt and have Bolingbroke in his place? I don't have a simple answer. Of course, potentially, if you could take out the whole of the House of Lancaster, there would be a huge amount of land and patronage to redistribute. Some ambitious lords may have dreamed of this possibility, but it was, as they say, a Big Ask.
Ironically it was Henry Bolingbroke who, by broaching this story, set in train a series of events that almost did destroy his House.