LONDON — A wildfire raged for a fourth day through dry grassland to the east of Manchester in the north of England on Wednesday, as Britain sweated through one of its hottest and driest summers on record. The blaze started on Sunday on Saddleworth Moor, an expanse of hills cloaked in purple heather that is popular with hikers and home to bird species including the endangered golden plover and curlew and the common red grouse. It has since spread over an area of seven square miles, and firefighters have requested help from the military. “It’s dry as a tinderbox up there,” said Brenda Warrington, leader of Tameside Council at a news briefing in the early afternoon. “A lot of wind is fanning the flames.” She said the situation was very changeable because wind had risen again in the area since the morning. Press Association via Associated Press Smoke from the fire could be smelled drifting over Greater Manchester, one of the largest urban areas in Britain. Southern parts of Europe have seen large expanses of dry forests ablaze during hot summer months in recent years, but large wildfires rarely hit Britain. “The scale of this fire is unprecedented, and we believe it may be the biggest in living memory,” Amanda Anderson, director of the Moorland Association, which works on preserving the highly prized landscapes, said in a statement, adding that gamekeepers who cultivated grouse on the moor for shooting had usually kept the risk under control.