A few weeks ago, the National Health Service was hit by a widespread and devastating cyber attack - Horizon tells the inside story of one of the most challenging days in the history of the NHS.
On the morning of 12 May the attack started. Appointment systems, pathology labs, x-rays and even CT scanners were infected - putting not just data but patients lives at risk, and on every screen a simple - some may even say polite - message appeared. 'Ooops, your files have been encrypted!'
But what followed was far from civilised. It was very clear that all the data on an infected machine was now scrambled and only the hackers could unscramble it. For a price - and with an extra twist - after a few days the ransom money doubled, and if nothing was paid within a week, the hackers threatened to destroy all the data - forever
Horizon is BBC Two's flagship 50-minute science documentary series.
Recognised as the world leader in its field, it regularly wins a sweep of international science, medical and environmental film accolades, and has recently won the Royal Television Society Award and the Prix Italia.
In 2002, the British Academy of Film & Television Arts presented Horizon with the BAFTA Television Award for Best Factual Series or Strand.
In 2003 it won the prestigious Images et Science award for best medical documentary and the Carl von Linne Award at the Living Europe film festival in Sweden. That year, a Horizon co-production with WGBH Boston won the Emmy for best documentary.
In September 2014 it celebrated its 50th anniversary and it continues to enjoy outstanding critical acclaim.