Were would the claimant file suit? MA or UK?
If they need to file suit in MA, I would find out the extent of injury and if the injury were mild, I would ignore the suit. I'm not a lawyer, I'm basically telling you what I would do. You have a lot of homework to do with UK law.
If they can sue in the UK, I would look into an attorney with UK law experience or find a law board like this over on that side of the pond.
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Homework for OP.
Were would claimant file suit?
What kind of injury did claimant receive?
At what cost is medical?
Is medical treatment done?
How did the cup fail? We know the handle fell off, but why?
You also have to stop this from happening again. I would have a lawyer write you something that tells everyone that has bought a cup from you that the handle may fall off and that hot liquids can burn. You need to recall your product to protect yourself.

