Scotland Yard 'lost' Roslyn Loveless's letter about Thomas Markle

One of the big questions around this Thomas Markle situation is "why didn't Scotland Yard share information with Mexican or American authorities?" The Met obviously found Roslyn Loveless's letter credible, credible enough to share with the Duke and Duchess of Sussex and possibly members of the royal household. So why didn't they share information with [ . . . ] Source