Three days ago I said that the Israeli government needed to give an account of how the deaths at the beach in Gaza had come about. On the basis of an internal military investigation, the IDF now says that they weren't caused by Israel (see the reasons set out here and here). Its suggestion is that the cause is more likely to have been a mine laid by Hamas. This report gives some reasons for doubting that, and cites the view of Marc Garlasco of Human Rights Watch that it was probably an artillery shell.
A room in south Manchester isn't the best place from which to try to resolve this. Just going on what I've read, I'd say that Israel needs to put the issue in the hands of an independent body. By 'independent', I mean of mind as well as of connections: not, therefore, a body composed of people who start with a fixedly one-sided view about the distribution of rights and wrongs in that region.