Revealed: Mandelson failed vetting but Foreign Office overruled decision

Guardian investigation uncovers decision by UK security officials to deny clearance before Mandelson took up role as US ambassador

• https://www.theguardian.com/politics/2026/apr/16/officials-debate-withholding-mandelson-vetting-documents-from-parliament">Officials debate withholding Mandelson vetting documents from parliament

• https://www.theguardian.com/politics/2026/apr/16/five-key-questions-decision-peter-mandelson-security-clearance">Five key questions: Who overruled the decision to deny Mandelson security clearance?

Peter Mandelson failed his security vetting clearance but the decision was overruled by the Foreign Office to ensure he could take up his post as ambassador to the US, an investigation by the Guardian can reveal.

According to multiple sources, Mandelson was initially denied clearance in late January 2025 after a developed vetting process, a highly confidential background check by security officials.