On 28 March 1795, Canning writes: "Saturday morning - Leigh [his uncle Rev. William Leigh] and Frere [John Hookham Frere, Canning's friend from Eton] and his father breakfasted with me, and we went together to see the Shakespear manuscripts at Mr. Ireland's in Norfolk Street, and we all agreed, I think, in believing so much as we did see to be genuine. What they prove, or whether they prove anything as to the genuineness of the new Play (Vortigson [i.e. Vortigern]) which Mr. I. asserts to have been discovered at the same time and in the same place with these papers, but which he does not shew - is another question. Vortigson, we understand, is not to be published until it has first been produced upon the stage."
This is very interesting for several reasons, not the least of which is the implicit uncertainty about the authenticity of the manuscripts. Also, the visit taking place on a Saturday morning is noteworthy: in the Prospectus for the printed edition of the papers, dated 4 March 1795, Samuel Ireland invites visitors "on Mondays, Wednesdays, and Fridays, between the hours of twelve and three." Clearly being an MP had its perks!
With many thanks to Aaron Pratt (@prattrarebooks), who kindly checked on ECCO for me, I can report that Canning and his companions are not listed among the subscribers to the folio edition of the Shakespeare papers, published early in 1796 (I only have the octavo edition, which doesn't contain the subscriber list). It's too bad we don't have Canning's journal for the year after his visit to Norfolk Street - it would be fascinating to know if he attended the first (and only) staging of Vortigern on 2 April 1796.