Executives from Royal Dutch Shell and Eni have met Iranian officials in Tehran to discuss investing in the country’s energy industry, the first time international oil groups have publicly confirmed such talks ahead of a possible nuclear deal with the west. The meetings, which took place in May and June, are evidence of the growing interest among big oil companies in Iran, which boasts the world’s third-largest oil and gas reserves but which will need tens of billions of dollars of foreign investment to realise its ambitions to nearly double production by the end of the decade.