There's a hipster/divey burger joint in London near Southwark station that does horse burgers, as well as lamb, wild boar and cow. Oh, the Lord Nelson - just found it.
https://www.lordnelsonsouthwark.com/about-us/
I wasn't going to commit to a 13GBP 1/2 lb horsey burger - but totally would have done a "tasting" trio of sliders, one of them being Mr. Ed. Meat is murder, and I'm OK with that. Especially horses after the cranky preschool glue-factory-bound pony bit me in 1978. I hold a grudge...