Cameron demands inquiry over 'unacceptable' jet ski shooting incident Although Gibraltar is self-governing, defence of the territory remains the responsibility of the British Government in London. Downing St said the Prime Minister made protesting to Mr Rajoy his first priority on arriving at the summit in Brussels on Thursday. Speaking to reporters after the European Council meeting finished, Mr Cameron said: "I have raised this with the Spanish Prime Minister. I think this is a totally unacceptable episode and I made that clear. I think it's very important the people of Gibraltar know that we support them, we support their sovereignty, we will always stand up for them and stand by them. I think its very important countries obey all the international rules, all the international laws. Downing St sources said Mr Cameron had told Mr Rajoy that Spain must hold a "full investigation" to establish what had happened. Mr Cameron said: "We need to find out more about exactly what happened but from all I've heard from the First Minister in Gibraltar, it's not acceptable and that's why I raised the issue. I think we can avoid these incidents in future. British sources said the Prime Minister sought out Mr Rajoy to raise his concerns. One source said: "He underlined the importance of a full investigation into what happened. He was very clear and very firm about it. I think they understand our views.