Big data. It's one of the tech cliches of the age. The idea that the torrent of data now being created can be processed in all sorts of clever ways with life-changing implications.
On my Tech Tent podcast this week, we look at the promise and perils of data and ask whether we are ready to share more of it with companies that say they will use it for our benefit....
But not everybody is happy about this deal. Some have questioned the circumstances under which this sensitive and potentially valuable data was handed over to a powerful technology company. Among them is Julia Powles, who works on technology law and policy at Cambridge University. She's concerned that the health service has struck a deal with Google, which has no experience in healthcare, and asks whether we would be comfortable if a similar arrangement was made with a drugs company.
DeepMind's co-founder Mustafa Suleyman tells us that the company has showed unprecedented levels of transparency in publishing the contracts it has with hospitals. He insists that doctors and nurses approached DeepMind with the idea for the app - and that the data cannot be used for any other purpose than improving the care of patients.