Blair announced in September 2006 that he would quit as leader within the year, though he had been under pressure to quit earlier than May 2007 in order to get a new leader in place before the May elections which were expected to be disastrous for Labour. In the event, the party did lose power in Scotland to a minority Scottish National Party government at the 2007 elections and, shortly after this, Blair resigned as Prime Minister and was replaced by his Chancellor, Gordon Brown. Although the party experienced a brief rise in the polls after this, its popularity soon slumped to its lowest level since the days of Michael Foot. During May 2008, Labour suffered heavy defeats in the London mayoral election, local elections and the loss in the Crewe and Nantwich by-election, culminating in the party registering its worst ever opinion poll result since records began in 1943, of 23%, with many citing Brown's leadership as a key factor. Membership of the party also reached a low ebb, falling to 156,205 by the end of 2009: over 40 per cent of the 405,000 peak reached in 1997 and thought to be the lowest total since the party was founded.

When did Blair announce he was quitting?