YouAintNoMuslimBruv has become Britain's top trending Twitter hashtag after a passer-by shouted the dismissive remark at a knife-wielding man in a London Underground station.
Police are treating Saturday's attack at Leytonstone Tube station in east London as a "terrorist incident".
In video footage, an onlooker is heard shouting "You ain't no Muslim, bruv" as the 29-year-old suspect, reeling after being hit with an electric stun gun, is pinned down and handcuffed.
The dismissive retort was the top trending hashtag in both London and the whole United Kingdom.
The male voice heard on the amateur mobile phone footage said: "You ain't no Muslim, bruv! You're no Muslim, bruv! You ain't no Muslim!"
AFP / 3 News