Unfinished and with its author unidentified, Thomas of Woodstock is often called Richard II part I as it focuses on the early part of his reign. It was read by the cast during preparations for Richard II, to help put the latter in context.
Assistant director Owen Horsley was then given the task of trimming the text down and directing this rehearsed reading with some of the cast (see cast list on the right, click for bigger version).
Although tonally different it does set up the Shakespeare play superbly. It was also the most polished rehearsed reading I've seen, including some specially written music by soprano Anna Bolton who performed with Helena Raeburn. The actors made entrances and exits, swapped seats or sat on the stage and generally moved around more than you'd expect from a rehearsed reading.
So, in Thomas of Woodstock there is much that helps to explain Richard's behaviour in Richard II, the latter picking up the story just after Woodstock's death or the Duke of Gloucester as he's called in Shakespeare's play. Richard is young and petulant but being under age it is his uncles and protector Woodstock who wield the real power - think patriarchs in a mafia family. However, the young King discovers that his uncles have mislead him about his age and therefore held the power for longer than they should.