I thought he had passed already as he had not been in the public eye. However, his death has just been announced. I am posting mainly on account of "Two's Company", the LWT sitcom that ran from 1975 to 1979 in which he combined very memorably with the American actress, Elaine Stritch. Donald Sinden RIP.
https://www.comedy.co.uk/news/story/000001600/donald_sinden_dies_90_never_the_twain_twos_company/