A farming group controlled by the Duke of Westminster is warning of “dramatic” rises in food prices due to spikes in fertiliser costs linked to the war in Iran. The closure of the Strait of Hormuz in the Gulf , through which large quantities of oil, gas and other fuels usually pass, has already led to jumps in fuel costs in the UK. This week, the British Retail Consortium (BRC) warned that supermarkets were already absorbing huge extra costs due to the conflict in the Middle East and said those costs would inevitably filter through to consumers. It wants the government to delay new tax and regulatory rules. Now, Mark Preston, the executive trustee of the Grosvenor Group, controlled by the Duke of Westminster, who is the godfather of Prince George, said costs for UK farmers are up by up to 70 per cent since the conflict began. That pain may not hit stores this year, as farmers are using up old stocks of fertiliser rather than the batches that have soared in price.…