Action thriller Olympus Has Fallen follows it at six, while at seven new release Mud took an impressive £237,000 from just 71 locations.
In these early January days of heavy grounds and sloshing mud it takes a significant effort to conjure something decent out of the ooze.
It's like swimming through mud: It takes a lot of effort and you don't get very far.
"When someone's trying to pull you down into the mud, it takes a lot less effort to give in and join them in the muck than to keep yourself upright, standing tall.
Mud takes its name from its lead character, played by Matthew McConaughey, delivering the best performance of his career (and his second at the festival, after The Paperboy) as a fugitive holed up on an island in the Mississippi after murdering a rival for his lover Juniper (Reese Witherspoon).
Conventional composting of press mud takes about 6 months, does not remove the bad smell completely, has less nutritive value and is compacted.
Nichols, one of the most acclaimed filmmakers of his generation ("Mud," "Take Shelter," "Midnight Special"), said in an interview that was captivated when he saw "The Loving Story," the documentary about the case.
But a recent research project that used core samples of mud taken from the Lake in Central Park showed a different pattern altogether.
They slide into the Arkansas mud, taking me with them.
He also urged that the removal of water from the contaminated mud take place on the river itself, "whenever possible," rather than on land, and urged careful monitoring to watch for any impact on residential areas and flood plains.
