Britain's pound has slumped after a so-called flash crash - with the UK currency already under pressure over Brexit fears. During Asian trading hours the pound crashed briefly to $1.1841, but has since recovered much of that ground. Analysts believe automated trading systems were somehow triggered, leading to a sell-off. It came after reports French President Francois Hollande is calling for 'tough Brexit negotiations'. Laith Khalaf of stockbrokers Hargreaves Lansdown says it was a short, sharp fall in pound sterling.