More than a million people in the UK now live with a condition that causes the heart to beat irregularly and can lead to strokes.
Data from the British Heart Foundation (BHF) shows the UK has, for the first time, topped the million mark in the number of people diagnosed with atrial fibrillation.
The figure is up almost 20% on five years ago. High blood pressure, heart valve disease and binge drinking are among the causes alongside the fact people are living longer.
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The Labour leader said socialist politics would not be put "back in a box" as he appeared on stage at the festival.
There are reports that at least some MPs and Lords have been left unable to access their emails as a result of the attack.
Cuillin, six, and four-year-old Lejla designed the memorial plaque to their mum that has been installed in the Commons chamber.