Britain joined the U.S. and its allies in the fight against ISIS -- but any mission will come with a huge price tag. The UK parliament has approved airstrikes in Iraq against the terror group which prime minister David Cameron has called one of staggering brutality. Cameron had said Britain should join international allies in combating ISIS, an action that he warned would take not just months, but years. While the total cost will depend on the intensity and length of operation, past experience can give some guidance, Malcolm Chalmers, research director from the Royal United Services Institute said. Chalmers pointed to the UK's seven month involvement in Libya through 2011, which cost around $390 million, including missiles and flight hours. The bill is additional to standard defense budgets, which include staffing costs and weapons spend. Last year, the UK defense budget was $60 billion. Chalmers said he would expect the cost of ISIS airstrikes to be in the ballpark, of the Libya operation, assuming we only use air power and the campaign lasts for a couple of years. Cameron has said that the mission against ISIS could last years. However, it is U.S.-led rather than the operation in Libya, in which European countries took the lead. ` Uniquemissiles Cameron, in Friday's debate aimed at convincing parliament to approve airstrikes, said Britain has unique assets no other