Here's the salient bit from the Wikipedia entry:
The Lascelles Principles are notable in that their formal statement was not incorporated in any governmental document, but rather was in the form of a letter to the editor of The Times by Sir Alan Lascelles, writing under the pseudonym "Senex", published on 2 May 1950:First, a fellow pseud!
To the Editor of The Times
Sir,—It is surely indisputable (and common sense) that a Prime Minister may ask—not demand—that his Sovereign will grant him a dissolution of Parliament; and that the Sovereign, if he so chooses, may refuse to grant this request. The problem of such a choice is entirely personal to the Sovereign, though he is, of course, free to seek informal advice from anybody whom he thinks fit to consult.
In so far as this matter can be publicly discussed, it can be properly assumed that no wise Sovereign—that is, one who has at heart the true interest of the country, the constitution, and the Monarchy—would deny a dissolution to his Prime Minister unless he were satisfied that: (1) the existing Parliament was still vital, viable, and capable of doing its job; (2) a General Election would be detrimental to the national economy; (3) he could rely on finding another Prime Minister who could carry on his Government, for a reasonable period, with a working majority in the House of Commons. When Sir Patrick Duncan refused a dissolution to his Prime Minister in South Africa in 1939, all these conditions were satisfied: when Lord Byng did the same in Canada in 1926, they appeared to be, but in the event the third proved illusory.
I am, &c.,
Second, the second point hits home. The wiki piece calls it "dropped from the canon", but there's a real argument to be made that Canada cannot afford another election. If it can't, and another government is in the offing, why not let them take a shot at it? It's not a "coup"—Paliament is still supreme and the House itself goes on—and it might be the only way of creating a government stable enough to last, since Harper is clearly willing to have as many elections as he can get away with.
Let's be honest. Mumbai is far more important in the broader scheme of things. But this Canadian thing is gripping; and it's only likely to get better.