Barrister Nicholas Wayne made the extraordinary argument in defence of his client, Brigadier Priyanka Fernando.
The soldier was caught on camera running his fingers across his throat while standing guard outside the Sri Lankan High Commission last year. The Brigadier left the country days later.
A British judge has since found him guilty of causing “harassment, alarm and distress” to Tamil complainants who brought a private prosecution, but the Brigadier claims he has diplomatic immunity.