Union boss Mark Serwotka told 5 live's Chris Mason that he is in "urgent need of a heart transplant" and at one point had to wear a battery powered device stitched to his heart to keep it pumping.

The device allowed him to live an "almost normal life", but he had to "plug [the device] into the car's cigarette lighter" and "plug into the mains at night"

Mr Serwotka's heart failure came after contracting a virus while walking his dog in the woods.

He said: "He came back smelling of something foul so I washed him down. The next day my face and legs had swollen grotesquely like an extreme allergic reaction. A week later I got rushed to hospital with a heart rate of 220 beats per minute.

"After six weeks of investigation it was established I had contracted a virus that caused my heart to massively inflame. When the swelling went down it had been irreparably damaged."