Friday's massive cyber attack has left countless NHS patients facing lengthy delays for crucial tests and operations.

And it even led to a worrying computer blackout during a heart operation, one surgeon revealed.

Grandfather Grant Gowers, 50, was one of those affected. He was due to have a prostate cancer biopsy yesterday morning at Colchester General Hospital in Essex. But late on Friday, staff rang to say it had been put back by a fortnight, the Daily Mail reports.

Mr Gowers, from Clacton-on-Sea, said: "They said nothing was going ahead unless it was life or death.

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"But to me, cancer is life and death - and I won't know whether or not I have cancer until the biopsy results come back."

Ray Neal, who had a triple heart bypass operation in 2015, didn't even get a phone call to tell him his vital scan was cancelled.

He was urgently booked in last week, after tests showed blood pumped out of his heart was making its way back in.

Yesterday he had travelled an hour from Wanstead to the Royal London Hospital in Whitechapel, only to be told it wasn't happening

He said: "I am fuming. When it's your heart - it's your life isn't it? It's really worrying. I want to know what's wrong with me. I just want peace of mind."

Meanwhile, a surgeon at nearby St Bart's Hospital told how computer screens flickered off during a heart operation. Luckily monitoring machines kept working.

And Martin Hardy, 52, was left in agony after an operation on his broken kneecap was delayed when the Royal London said his case was not urgent enough.

Mr Hardy said he would like the cyber-criminals to "experience being in my position".