Guardian says Britain made it destroy Snowden material | Reuters

From this article:

Rusbridger said the destruction of the computer material was "pointless" as there were other copies of what was lost, and it would not stop the Guardian from pursuing Snowden stories.

"We will continue to do patient, painstaking reporting on the Snowden documents. We just won't do it in London," he said.

A British source with knowledge of the security services said GCHQ had no powers to seize material from the Guardian, but could have accused the paper of possessing stolen materials and demanded they be destroyed.