On 25 June Cheshire was tasked with a daylight raid against the Siracourt, a storage bunker and launch site for V-1 flying bombs made of reinforced concrete buried in the earth. Cheshire had lost his Mosquitos, as another squadron asserted a prior claim on them. Desiring a manoeuvrable replacement aircraft to mark the target, he thought a Mustang ideal, but he knew he would never get the Royal Air Force to go along with giving him one. He obtained one from the Americans instead. The aircraft arrived boxed up in its packaging crate the day of the evening he was to fly the mission. Flying the Mustang posed a number of problems for him, as he had not flown a single-seat aircraft since his training days. His major problem, however, was working out a course to the target. He had never flown without a navigator, and now he found himself in the position of having to ask for help. He asked for the squadron's navigators to help him work out a course, while his ground crew put together the Mustang. His ground crew finished the job by late afternoon, some two hours after the Lancasters had taken off. With no time for a test flight, off he went to chase down the Lancasters. The machine worked beautifully, with Cheshire arriving over the target just as the high illumination flares were ready to be dropped. He marked the target, and the Lancasters landed three Tallboys on it, destroying it utterly.