I've not been to this, but I do think that this brewery has stepped up their game since I first tried one of their beers so this sounds like an interesting and fun event for those who are able to go: "IT'S THAT TIME! We're brainstorming new and unique casks to debut at our 2019 Cask Festival! We're tapping over 20 specialty casks - some traditional favorites, like Oatmeal Milk Stout with mint & vanilla and Special Ale with chocolate and chillies.. but also many NEW creations that we've never tried before. So get ready to be blown away! Full list of casks TBA." More details here: https://www.eventbrite.com/e/2019-river-horse-cask-festival-tickets-53161041105
I've been to a few of these before and they are all casks of River Horse beers. Nothing mind blowing, but the first time I went they had a coffee version of their oatmeal stout which is probably the best beer they've ever produced IMO.
I'll agree with @drtth that Riverhorse has improved. I think they've even had several levels of improvement; the stuff they put out when they opened was not very good. Their newest brewer who came in about 2 years ago "seems" to have been the best but I haven't really kept up that much - first impressions matter! I also agree with what I thought @jmdrpi was implying... 20 casks from Riverhorse doesn't excite me that much. A properly done cask is not an easy thing to do and I wonder if these are just casks filled with regular beer and hop/adjunct bags which is so common these days. Still, it might not be a bad event, especially if you live close or are in the area for some reason.