Experts have unearthed evidence in the remains of Chester Amphitheatre which suggests gladiators appeared there.
Well, yes, of course gladiators appeared in the amphitheatre. That's what happened in amphitheatres. Why should anyone ever think differently?
The next paragraph sheds a little more light - "It was previously thought the arena was only used for ceremonial activities" - but in fact you need to go to other reports to find that what this refers to is the notion that amphitheatres in Britain were only used for military parades and training.
Personally, I've never bought that. The only argument in favour seems to be that amphitheatres in Britain, such as those at Caerleon, Chester, and London, are often associated with forts or fortresses. But for a start, at least one isn't (Silchester). And in any case, an association with a fort doesn't prove that gladiatorial games didn't take place there. If you found a football field in a modern army base, you wouldn't conclude that, because of the military association, no-one actually played football there. I'm more than happy to accept that ceremonial events and military activities did take place in amphitheatres in Britain (after all, modern football stadia are used for activities other than football matches, such as pop concerts), or even that the Roman army paid for those sited next to forts. But I have never seen a convincing argument that these buildings were not used for the same purposes for which amphitheatres around the empire were built.
I wonder, as well, if there isn't a bit of cultural snobbery behind the military theory. It used to be suggested that the Greeks in the East weren't interested in gladiatorial games, because they didn't in general build amphitheatres - the subtext being that the culturally educated Greeks were above such vulgar Roman entertainments. The problem is, they weren't - what happened was that instead of building new specialist amphitheatres, already existing theatres and stadia were converted for gladiators. So I wonder whether in the past, British archaeologists wanted to think that ancient Britons, our noble ancestors, would have no interest in the spectacle of men killing each other. But it's now clear that the Britons loved it as much as anyone else in the empire, and I for one have never believed otherwise.