Sounds a lot like the Great Peshtigo fire which happened at exactly the same time as the Great Chicago Fire, which some attribute to Comet Biela.
Found a good summary of the comet/540AD discussion here: Baillies Comet & Gildas
BTW, analysts think that St. Gildas may well refer to more than one individual, but so little is known about the fellow (that pesky Dark Age saw so terribly many things burned) that it is a merely a scholarly thing to place his birth at 500 AD rather than earlier or later.
I think it most interesting that he wore a single garment, had 24 brothers over beyond the Wall, and otherwise preached extreme pacificism.
Worth noting ~ why Gildas delayed his writing was because he'd gone to Rome just before the event. What had been an easy trip in 534 was abysmally disastrous in 536. He reports of what he saw on his way back and it does sound like he went overland from Rome to Britain.
Shortly afterward you find King Ad giving away the family farm to the Saxons ~