He had the drives destroyed after noting to the Whitehall guys that it would do nothing: "a peculiarly pointless piece of symbolism that understood nothing about the digital age."
It was probably a compromise after the spooks asked for the disks to be handed over.
Destroying them doesn't prevent the data from being in other places but it prevents that copy of the data from getting into other peoples hands e.g. what happens if those laptops get stolen?
http://www.theguardian.com/commentisfree/2013/aug/19/david-m...
He had the drives destroyed after noting to the Whitehall guys that it would do nothing: "a peculiarly pointless piece of symbolism that understood nothing about the digital age."