LONDON — Alan Rusbridger, the mop-haired, soft-spoken editor of The Guardian newspaper, finds himself in a shadowy battle with the British government over purloined secrets that the government will have a hard time winning in the Internet age.

The Guardian, which leans left and used to see itself as the voice of Britain’s socially conscious middle class, has struck a more combative tone in the last few years. It was deeply involved in publishing the WikiLeaks material and with that organization’s impresario, Julian Assange, and now Glenn Greenwald and t Edward J. Snowden, the former National Security Agency contractor who leaked classifed information to Glenn Greenwald, ablogger for The Guardian.

Having gone global and remained free to readers on the Web, with a newsroom in New York as well as in London, The Guardian is a much harder news organization than most to intimidate or censor, as the British government, with no written constitution or bill of rights to enshrine protections of free speech, has discovered.

But the tale of the last two months, as Mr. Rusbridger tells it, at least, is an extraordinary one of attempted political interference. Agents of the British government descended on The Guardian’s offices to monitor three executives as they physically destroyed computer hard drives containing some of the classified material that Mr. Snowden downloaded from American intelligence databases and gave to Mr. Greenwald and others.