A man shouting and holding knives has been tasered by police outside Buckingham Palace.
The drama unfolded as hundreds of tourists and Londoners gathered to watch the changing of the guard.
A warning - Nick Thatcher's report contains footage that some viewers may find upsetting.
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Muslim leaders condemned the "heinous and appalling" Westminster terror attack.
Travis Frain is recovering in hospital and has posted a photo to Twitter of Prince Charles by his bedside.
Acting Commissioner Craig Mackey led new policemen and women in paying their respects at a passing-out parade in Hendon, north-west London.