Additionally, Teribus, the ship was not in actual or claimed Israeli water. It was in Lebanese water (earlier international water). So an Israeli attack on it would most clearly have been an act of war by Israel against the UK - as the German sinking of American vessels (WWII) (and WWI) upon the high seas was an act of war by Germany against the USA. The point I was making was not whether the UK would have declared war upon Israel but that Israel would have carried out an act of war against the UK.