The Canadian pianist has been giving illustrated lecture recitals on Bach performance for some time but not, on this showing, direct to camera. Though she becomes more fluent and confident over the 148 minutes, for most of the time she resembles the Queen delivering her Christmas message to the Commonwealth. Is she reading off an autocue? Her measured and articulated delivery with nary an “um” or “er” suggests that she is; if she isn't, then it sounds as though she is, and reading a script which, moreover, has been written to be published in a book rather than spoken aloud.

Its seven chapters are divided into 36 sections, each one fading to black-out and up again: usefully cued but tiresome to watch. The whole exercise would have been better on CD. What Hewitt has to say is full of wisdom and perspicacity, liberally illustrating the talk at her Fazioli piano (it is filmed in the Fazioli factory where “[the] high level of craftsmanship in piano manufacturing is, in my opinion, unsurpassed”). But who is it aimed at? The conservatory student (useful), the teacher (instructive), the amateur Bach player (daunting) or the general public (illuminating but esoteric)?

Disc two is a live recital filmed in the Fazioli concert hall where Hewitt puts into practice what she has been preaching. If I prefer my Bach - well, any composer come to that - without facial expressions and (some surprisingly) theatrical gestures, one simply listens spellbound. Hewitt's poise, clarity of voicing, spontaneity, wonderful finger legato and palpable joy in performing these works is a masterclass in itself.