I think the marbles should be given back to Greece as a gesture of goodwill. Perhaps they'll then give us something in a likewise gesture. We are supposed to be friends after all, & this is a sore point between us.

Regarding the history of colonisation generally:
Well, it was totally horrific. I suppose we gave the colonies three useful things: railways, the English language, and most importantly - cricket. In return they got centuries of slavery, relentless oppression, and ruthless asset stripping. I do not think we can ever really consider the idea of reparations because (1) they were different ages with different moral zeitgeists (2) the cost would be astronomical or beyond computation.