Wikipedia:Articles for deletion/Ralph de Greystoke, 5th Baron Greystoke
passes  as the subject is discussed in the Oxford Dictionary of National Biography entry cited in the article. I've seen the entry, it is clearly significant coverage and goes into detail about the subject's life and their role in the conflicts of the period (695 words are devoted to the subject specifically). I can only assume that "content is not available at that source" means "the source is not available for free on the internet to everyone", but there certainly isn't any policy or guideline against the use of such sources and they are widely used. Sources do have to be ''published'', but the ODNB is and I was able to read this entry for free with a library card
— User:Hut, 19:15, 5 May 2015 (UTC)
Stance: keep
Cited policy: WP:GNG (Wikipedia:Notability)