He was an outspoken advocate for the independence of India at a time when the Indian cause lacked effective voices within England.

[4][5] He was president of the Society for the Prevention of Premature Burial and left instructions that when he died his heart should be cut out.

He resigned over his advanced age but also because Ada Cole had been dismissed from the Society for investigating the cruelty and slaughter of British horses being exported to Belgium.

[9][10][11] He disagreed with exporting horses to Belgium for slaughter and commented that "I have been a member of the council for many years... and do not agree with the line they are taking on many subjects".

[19] Greenwood died a year later after what Henry S. Salt described as a "stormy meeting of the RSPCA that heralded his final and fatal illness".

[18] Greenwood was also one of the most persistent and effective fighters in the Shakespeare authorship question, and published many books on the subject.

In 1922 he joined with J. Thomas Looney to establish The Shakespeare Fellowship, the organisation which subsequently carried forward public discussion of the authorship question up to the 1940s.

[21] I cannot help the belief that, as thought and true civilisation advance, it will be recognised that to seek pleasure in the hunting of any animal to its death is unworthy of a thinking and humane man.