Family of a New Zealander killed by a falling tree branch at London's Kew Gardens two years ago is concerned about the reason given for the incident.
An inquest into the death of Erena Wilson at the gardens on September 23, 2012, has heard the reason Kew gave for the branch falling on Wilson was bad weather, while the family believed it was caused by a known phenomenon called summer-branch drop.
Wilson, from Wellington, died when a "catapulting" branch of a cedar tree and hit her while she walking in the gardens.
An arborist acting for the family has told the inquest at West London Coroners Court, that summer-branch drop was a risk similar to avalanche or rip tides.
John McLindon, acting for the Wilson family, said the family believed Kew arboretum head Tony Kirkham should have said in his report on the incident, and in interviews with investigating body the Health and Safety Executive, that summer-branch drop could have caused the fatality.
Instead Kirkham's report said: "The trigger was a squally wind from a northerly direction, an unusual direction, and heavy rain."
Kirkham had told the court 50kmh wind gusts and 5 millimetres of rain in the previous hour had caused the branch to fall.
McLindon said the summer-branch drop phenomenon was identified in 1979 by a tree expert called Rushforth and Professor Richard Harris had given a lecture in 1982 in which he said Kew had entrance signs warning of branch shed.
Kirkham said he could not remember the signs and neither could his predecessors, but they may have referred to branches dropping after the 1976 drought and because of Dutch Elm Disease.
McLinden argued that potentially hazardous areas should be roped off and there should be website warnings and signs.
He cited an interview in British trade magazine Horticulture Week in July 2012, two months before the accident, in which Kirkham said cedars were among the trees that suffered from summer-branch drop because of "fantastic" growth that year.
Kirkham said he hadn't known of particular instances at Kew and his statement had been to warn "people to be wary".
Kirkham admitted some errors in Kew's tree maintenance record-keeping.
The cedar tree involved in the incident was last pruned in 2000 and was on a 10-year maintenance cycle but Kirkham said Kew had a prescriptive policy for pruning rather than the regular "haircuts" McLindon suggested were necessary.
"You can't totally mitigate the risk of branch failure even from pruning," he said.
Kirkham said Kew had improved record-keeping since 2012.
"I still believe what we did was right and following inspections we carried out to that tree it was deemed no further pruning was warranted," he said.
The court heard there was a fatality at Kew in 1951 caused by a tree, and that more recently an empty pushchair had been hit by a falling branch.
Kirkham said there were two recorded instances of the phenomenon in 2013 at Kew and about 20 incidents in the last 25 years.
McLindon said Kew's approach to warnings was "outdated" because it was a "doctor knows best" approach.
Kirkham replied: "I still don't believe that signage would deter people from walking under trees and prevent something like this accident from happening."
An external audit of Kew reported staff saying "tree inspections at Kew suffered from a lack of resources" and McLindon suggested it was a matter of "luck" the cedar was inspected, but Kirkham denied that.
He said that of 10 secondary characteristics of summer-branch drop, the cedar displayed just three.
He told Patrick Blakesley, acting for Kew: "I don't think any other organisation in the UK is doing tree management to the detail we do."
Independent court tree expert Dr David Lonsdale told Coroner Elizabeth Pygott the tree's failure was "not completely typical of what might be regarded as summer-branch drop".
"It was akin to summer-branch drop but could not be attributed specifically to that cause," he said.
Asked if Kew could have prevented the accident, he said: "I don't think in the case of this particular tree there were actions that could really have been taken.
"There was something about that branch that caused it to fail but that can only be seen with hindsight."
Lonsdale said summer-branch drop was poorly defined in science.
He said warning signs were not necessary under Health and Safety Executive guidelines where a one-in-a-million chance of death was a "tolerable" risk, because the phenomenon was so rare. Kew had had one tree fatality since the death in 1951, in which time it had had about 60 million visitors.
Blakesley said that in general Kew had "very well-managed trees".
Yesterday, Wilson's friend, Tessa Marshall, who was with her when the accident happened said it was lucky she and her three-year old daughter were not killed by the falling branch too.
The inquest continues and the coroner is expected to sum up on Monday.