The death of a woman killed by a falling tree branch at Kew Gardens was a tragic accident, an inquest found today.

The jury at West London Coroner’s Court concluded New Zealander Erena Wilson, 31, from Hanwell, died from multiple head injuries as a result of the accident on September 23, 2012.

Coroner Elizabeth Pygott expressed her condolences to Ms Wilson’s family and described the accident as “ghastly”.

She said: “It was a ghastly accident and a ghastly affair for everybody.”

The accounts manager died after being hit by a large Lebanese cedar tree branch while visiting the Royal Botanical Gardens with friends for a child’s birthday party.

The inquest explored the possibility that natural phenomenon summer branch drop caused the death but the jury found there to be insufficient evidence to establish the reason the branch fell.

During the inquest, John McLinden QC said it had been a “fluke” that friend Tess Marshall and her daughter Ruby had not also been hurt, referring to how she had walked on ahead when her mother “could have easily been carrying her”.

He also questioned why Kew had not displayed warning signs, either near affected trees or at the entrance, but this way dismissed by head of the arboretum Tony Kirkham, because the risk was so minimal.

Mr Kirkham, who has held his position for 13 years, said he did not believe summer branch drop was the reason the branch collapsed.

Jeremy Barrell, a tree expert called by Ms Wilson’s family, told the court this was “definitely summer branch drop” and suggested the death could have been prevented if the tree had been pruned.

But coroner Pygott said: “Summer branch drop is a poorly defined phenomenon and I do not see how any prevention of future death report made by this court can help understand this phenomenon.”

The inquest was postponed from October when the coroner asked for further information relating to summer branch drop, which happens after long dry spells followed by heavy rain, the inquest heard.

Giving evidence, Ms Marshall said she heard a “crack like lightning” before running away and seeing Ms Wilson lying face down on the ground.

Speaking after the verdict Richard Barley, director of horticulture at Kew, said: “The jury found no identifiable cause of branch failure from this tree which caused this tragic accident.

“We, of course, continue to extend our greatest sympathy to the family and friends of Ms Wilson as a result of this tragedy.”

He added that it would have been inappropriate to place warning signs because it is “such an unlikely thing to happen”.

He said: “We are not talking about summer branch drop, we are talking about the loss of a limb from a tree with a tragic outcome.”

Ms Wilson’s parents, Chris Wilson and Elizabeth Shelley, remained in New Zealand throughout the inquest but called for further research into summer branch drop in a statement.

They said: “If one death could be prevented and one family spared from going through this then some good would have come from this tragedy.”

The large cedar of Lebanon tree was one of the originals planted in 1759 when the gardens first opened.

A verdict of death by multiple injuries was reached unanimously by the jury, who also concluded it was an accident.

Richard Barley, director of horticulture at Kew, said: “We welcome the conclusion of the inquest and hope that it has provided some measure of relief for all involved.

“We are reassured that the coroner appointed independent expert, Dr David Lonsdale, found that our tree management system is robust and that there were no reasonable means by which the tragic accident could have been prevented.

“We are deeply saddened by the death of Ms Wilson, and continue to express our sympathy to her family and friends.

“We would like to reassure our visitors that their safety remains of paramount importance to us. The probability of a visitor coming to harm at Kew as a result of a falling branch is exceptionally low.”