This video shows Dame Helen Mirren, dressed in her costume as the Queen, confronting the drummers outside the Gielgud theatre in London.
The footage was filmed by comedian Chris Dangerfield who lives in Soho.
More top news
In a wide-ranging Peston on Sunday interview, he said Parliament security needs reviewing and the PM's counter-terror strategy is flawed.
The terror attack carried out by Khalid Masood at Westminster that left four people dead lasted less than two minutes say police.
Two knives were found at the scene in Islington, North London, and the suspects fled on foot before being arrested.