Mystery Fire

What's the story? This site of a mysterious fire was found deep in Wood Crates , well away from any roads or occupation, under a Beech tree adjacent to an old infrequently used woodland track. It appears to have burnt intensely at its core, leaving little remaining other than a linear trench of fluffy ash. The fire had spread amongst the surrounding leaf litter, but with no real power it hadn't the strength to take hold, and had burnt itself out without much damage. There's no sign of human intervention nor any signs of human presence in the vicinity; so how did it start ? Does this mark the spot of a lightening strike? What ever its cause, with all the dry weather we've had of late, it could have been disastrous.