Before anyone gets confused, this Henry IV only has one part, lasts a mere 100 minutes, including an interval, and is not by Shakespeare.
Pirandello's Henry is a reflection on madness and uses its protagonist's struggle to regain and hold sanity as a metaphor for us all. Like Six Characters in Search of an Author, which was written during the same manic five-week creative period in 1921 and Absolutely! {Perhaps}, it is never quite what it seems and can leave its audience thoughtful or baffled by turns.
Michael Grandage's production, simply designed by Christopher Oram, brings the staging of the play up to date, although that is rather misleading in the context.
Henry IV, wonderfully portrayed by Ian McDiarmid, is a rich man now around 60. Twenty years before, in a pageant he fell from a horse and suffered a blow. This induced the belief that he had become his pageant character, a medieval king of France. Tyrannically, he forces all of those around to humour him by playing parts in Henry IV's life.
The first half of the play can be a little flat after an amusing and intriguing start when four medieval servants appear for a post-modern discussion about themselves and their master. We are then thrust into the modern day as Henry's former lover and her ineffectual husband, played by Francesca Annis and David Yelland, return after twenty years to see the invalid, bringing with them a psychiatrist who hopes to effect a cure.
They are forced into the fancy dress and have to humour the king. He is in a period of self-reproach and suffering, dressed in sackcloth and with crosses of ash on his cheeks.
The play really comes alive after the interval as Henry first becomes regal and then sane. It becomes clear that while he was genuinely mad for a dozen years, for the last eight, he has been toying with everybody. This allows him (and Sir Tom Stoppard, a master of the subject) to expound on a philosophy of life, reality and madness.
Ian McDiarmid is particularly good in the title role when the "magnificent madman" sheds his weakness, making fun of his visitors. From there, he moves into a solo debate about the freedom that madness gives to its victims.
As so often, Pirandello is no respecter of theatrical form and that is his strength. At the end of what is a fascinating and highly intellectual play, he characteristically leaves his audience with something of a mystery that will provoke much debate.