In 1974, at the funeral of his cousin Dominic Elwes who had committed suicide, after a sententious speech by John Aspinall, Rennell infamously "went up and gave  Aspinall the most useful punch in the face you have ever seen." He succeeded his uncle as 3rd Baron Rennell in 1978, and took the Conservative whip in the House of Lords.
In 1974, at the funeral of his cousin Dominic Elwes who had taken his own life, after a lengthy and pompous speech by John Aspinall, Rennell infamously delivered a powerful blow to Aspinall's face. He succeeded his uncle as 3rd Baron Rennell in 1978 and became the Conservative whip in the House of Lords.