I still do the exercises; got my book in 1981. I too was going to post that piece about Helen Mirren, as well as advise you ask your physician before starting them. I find they keep me feeling flexible and good; it's very basic, but it works. Good luck with it!
They were originally created for office staff of the CRAF.
I have the book and have done them periodically over the years.
However they stop at age 60. I am 76 and would like to start doing them again. Am a bit worried though. Does anyone else in my age group do them regularly?