WhatsApp took to Twitter to complain about the problems with the instant messaging service, while others joked that the app's recent multi-billion dollar deal with Facebook was behind the two-hour outage.
WhatsApp undergoes some downtime, as founders are too busy counting out their Facebook billions one bill at a time
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Government ministers from the UK, France and China attended the event.
Tonight investigates the increasingly sophisticated methods criminals are using to target the elderly and defraud them of their savings.
If you've been anywhere near Trafalgar Square today you'll notice something different.