Specifically which leaks harmed "national interest" without benefit to the public? I ask non-rhetorically, as GCHQ at least have shown themselves not to be above "leaking" carefully selected titbits and attributing them to Snowden, just to muddy the debate:

http://www.independent.co.uk/news/uk/politics/exclusive-uks-...

and the Guardian's "haha what":

http://www.theguardian.com/commentisfree/2013/aug/23/uk-gove...

Note that this "leak", as well as NOT coming from Snowden, isn't really in the domestic public interest, is an activity that a far larger percentage of people would support, and presumably is already known by the target anyway. The clear intent is to make people read the article and go "huh, this Snowden ballyhoo is very overblown". I wonder why the so-called "Independent" played along.