Above are the slides from the Topics lecture on 3 December. Below is a
list of the footnote exercises, together with clarifications and hints.
A version of this article was published by Springer in 2017 in the book
Special Metrics and Group Actions in Geometry and provided
images and other material exploited in the Topics lecture.
The latter is an out-of-print book published by Longman in 1989,
effectively a collection of lecture notes, emphasizing representation
theoretical aspects. It predates the much more detailed and analytic
texts by Dominic Joyce, published by OUP.