Where did Anouilh acknowledge that his play Becket contains many historical inaccuracies?

Question

The French playwright Jean Anouilh wrote the play Becket or The Honour of God / Becket ou l'Honneur de Dieu inspired by Archbishop Thomas Becket's conflict with king Henry II. (In 1964, five years after its premier on stage, the play was adapted into a film starring Peter O'Toole, Richard Burton and John Gielgud.) The Wikipedia article about the play contains the following unsourced statement:

It contains many historical inaccuracies, which the author acknowledged.^{[citation needed]}

The corresponding article on the French Wikipedia makes no mention of these inaccuracies. The Spanish Wikipedia article makes the same claim about the historical inaccuracies, again without providing a source:

Contiene muchas inexactitudes históricas, que el autor ha reconocido.

(This translates to the same sentence quoted above from the English Wikipedia article.)

Assuming that the statement has not been made up, where did Jean Anouilh acknowledge that the play contains many historical inaccuracies.

Answer 1

I believe Anouilh hints at this in the preface to the play:

Je n'ai pas été chercher dans les livres qui était vraiment Henri II - ni même Becket. J'ai fait le roi dont j'avais besoin et le Becket ambigu dont j'avais besoin.

My translation:

I haven't gone reading books about who Henry II really was - nor even Becket, for that matter. I have created the king that I needed, and the ambiguous Becket that I needed.

In the essay "Le thème de Thomas Becket dans Becket ou l'honneur de Dieu de J. Anouilh, et Meurtre dans la cathédrale, de T. S. Eliot" in Bulletin de l'Association Guillaume Budé, nr. 23, 1964, Marguerite Rabut writes that the same book was the source of both Anouilh's and Eliot's work: Histoire de la conquête de l'Angleterre par des Normands by Augustin Thierry, published in 1856. Rabut finds that Anouilh's play comes close to the facts described by Thierry, and, if there is any discrepancy, it would be one of emphasis rather than of fact. However, the description of Becket by Thierry is clearly flawed, and at some points completely wrong. Rabut does not mention whether Anouilh based his characters on Thierry's work in good faith, or that he could have known that it was problematic.

In any case, from the tone of the Preface, Anouilh does not seem to care one way or the other.