it's just pretext. The obvious answer is, let the parties in question figure it out. I'm sure they'll come to an agreement on how to share custody of historical artifacts as long as they come back home rather than stay in Britain.
Art and historical objects circle through different museums all the time, it's not a new concept. "Gosh I plundered something from India or Pakistan, oh my whoever will I give it back to?!" isn't a serious issue
mate I know who India and Pakistan are, there's a difference between zero sum conflict between both countries and getting colonial artifacts back from Britain. You'd be surprised how easy agreement on the latter would be.
Timeless.