MI5 Director-General Ken McCallum said in his annual speech on Tuesday that Iran is ramping up attempts to strike sensitive military targets in the UK. He revealed that 50 arrests were made in the past year to disrupt Iran-led operations. McCallum's warning follows UK Prime Minister Andy Burnham's statement that Iran's IRGC was "almost certainly" behind a suspected plot against RAF Fairford, which led the US to withdraw military jets from the base. Tehran has denied all accusations.