This morning, the former boss of the Foreign Office, Sir Philip Barton, will give evidence to MPs on the Foreign Affairs Select Committee, who are looking into the Mandelson vetting scandal. After that, the PM's former chief of staff, Morgan McSweeney, will also be grilled by the committee. It was McSweeney who advised Starmer to appoint Peter Mandelson in the first place. He resigned as the PM's right-hand man in February as pressure grew over the scandal. That session could prove blockbuster.