I’m not, in the normal run of things, a huge fan of obscure bel canto operas. A very long list of them languish in obscurity for very good reasons. So, my hopes were not all that high when I stuck the 2015 Glyndebourne recording of Donizetti’s Poliuto in the player. I was wrong. This is probably the best martyrdom opera from Glyndebourne since Peter Sellars’ production of Theodora in 1998.