Mobile chest X-rays just aren’t as good, especially on the larger patient, and it would be difficult to justify doing one on the basis of the patient wanting to keep it secret rather than clinical need. I imagine it would be quite a faff too to transport the equipment and the (incredibly busy) radiographer rather than, as a pp said, whip him in with police escort and bundle him back again after 15 minutes in radiology. If they want to CT him then the InHealth van pulling up in Downing Street wouldn’t need a press release to gain attention.