as with Savile and Maddie (not at the same time, of course) they have to investigate everything, and be seen to do so. Too many accusations, especially regarding Savile, have been prefaced by "I reported it but police weren't interested."
I can't see this as any more than just another claim for the mets 'ere Fred we've got another one in' file.
I'm not sure he is remembering anything much, some letter written by some soldier some years back. He's just hoping to get some attention I think, but with no real substance.