The Fossilised Tree at the heart of the Bryn Celli Ddu long barrow on Druidic Anglesey

But, a fossilised tree takes like twenty million years to create...

So, the possibilities are that the fossilised tree at the heart of the Bryn Celli Dud long barrow on Anglesey is:

a) a found object that bridges the wood=living stone=death belief systems of Megalithic Monument Builders 

b) a purposefully engineered object* that was intentionally grown in this way over a vast period of pre-historic time

c) a combination of the two where the petrification of the tree trunk takes place in highly-acidic high-silicate environments, again just for this purpose, which speaks of a High Technology of Tree Petrification for religious purposes.

Click the time-stamped image (below) to go to the relevant discovery in Rupert Soskin's Standing With Stones series. Later in the same episode, Soskin makes another gem of a discovery, linking a five-slotted stone at the centre of the Irish stone circle of Castle Ruddery with an identically five-slotted stone at the centre of the Dartmoor stone circle of Fernworthy.

For example: would the FIVE BRONZE SWORDS of five bronze-age kings or tribal leaders fit into these five stone-drilled slots, and is this the origin of the Arthurian myth of the 'sword in the stone'?

* PURPOSEFULLY ENGINEERED OBJECT: there's a similar reference to inverted tree within a wooden henge or circle at a place known as Seahenge at Holme next the Sea in Norfolk, as excavated at low tide by Francis Pryor and the Time Team. High acidity, high silicate environment - was this another attempt to create a petrified tree trunk pillar of stone?