If you’re buying a ticket for a film subtitled ‘Ragnarok’, chances are it’s not a first date. And you’ll probably have seen most of the 17 Marvel Studios films that precede it. Worry not, Thor’s third solo outing, under director Taika Waititi, is every bit the enjoyable romp the trailers suggested. Flash Gordon’s alive (!) again, with more whizz-bang digital effects and so many gags, it almost qualifies as a comedy. So where are we?