The Chief Secretary to the Treasury narrowly missed being pelted himself as he left the Royalty Theatre, in the West End, after addressing LSE students there.
Scotland Yard confirmed later that two students had been arrested. They were cautioned and released without charge.
Mr Portillo, who was invited to speak at the theatre by the LSE's Conservative Students Association, was jeered and heckled throughout the meeting.
Earlier this year, John Patten, Secretary of State for Education, was hit by an egg at the LSE, and Peter Lilley, Secretary of State for Social Security, was covered in flour during a recent engagement there.Reuse content