As a typical cynical Brit, I think it'd be a good exercise to one day make a list of all the people to whom the UK technically owes an apology, but not to actually say sorry until we get an apology from everyone that we feel owes us one. And yes, that includes you, Italy - don't think we've forgotten that little hoo-ha between Boudicca and Paulinus! It may have been the first century AD, but some scars just never really heal.
Oh, and if I come across as crass, it's because the whole notion of the thing is absurd. History is history - we all routinely did some horrifically awful things, but we don't do them now and no-one's seriously suggesting that we should.