The road was blocked from around 5am after the branch fell onto the top of the wall and into the road just outside the main entrance to the park.
Ric David from Guernsey Tree Services was called to the scene to assist emergency services at 6am.
He estimated the large oak tree the branch snapped off was more than 25 metres high.
‘At this stage we don’t know why it fell as there is no obvious sign of damage and it wasn’t windy,’ he said.
He added that the tree could have been damaged in winds on Wednesday morning, that included gusts of 45mph.
‘The tree is very heavy and full of leaf at the moment. Branches falling in this way is a phenomenon called sudden branch drop syndrome.’
Sudden branch drop syndrome, sometimes called summer branch drop, is the sudden, unexplained failure of large, healthy-looking branches from mature trees, often on calm, hot, humid, or wet days.
While the exact cause is unknown, theories include high internal humidity, water stress from a sudden downpour after a dry spell, internal tissue cracking and shrinkage from heat, or the weight of water on the canopy.
Work to remove the branch was delayed until a crane could be brought in to lift the branch away from the wall.
‘The wall has held up amazingly well and is only damaged near the top,’ said Mr David.
‘We have had to remove a couple of other branches that were damaged but at first look the tree itself looks like it is okay and should recover.’
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