In 2008–2009 he went on secondment to UK telecoms regulator Ofcom, returning to the Cabinet Office to lead the Smarter Government white paper.

In 2010, he was briefly made acting head of the FCO after Sir Peter Ricketts became the UK's first National Security Advisor.

He transferred to the permanent secretary role at the newly created Department for International Trade, until he left the civil service in March 2017.

[5] Donnelly led work to improve inclusion and gender balance across the senior civil service leadership in a range of departments.

In February 2018, speaking on Radio 4's Today programme, he warned that Brexit would be "giving up a three-course meal… for the promise of a packet of crisps in the future.