Wade said his phone has been running "red hot" with worried calls from local authorities after a five-year-old girl was killed while playing on a zip line at Mile End Park in Tower Hamlets over summer. Alexia Walenkaki was killed on 17 July when the tree trunk the zip line was attached to collapsed on top of her. The Health & Safety Executive (HSE) is now investigating the case, with its findings due out in 2016.
In September the HSE also released the results of its investigation into an April 2014 incident in which a seven-year-old boy suffered life-threatening injuries after the wooden pole of a rope swing he was playing on broke and hit him on the head. Although the boy recovered, self-employed safety inspector Glynn Hughes was prosecuted and fined for failings in his testing process. The HSE found Hughes had not identified that the swing was rotting during a number of inspections, marking it as low-risk just seven weeks before the accident.
The HSE, the BSI and insurance companies recommend trees and play equipment be inspected regularly, but Wade expects there will eventually be a push for stronger legislation. He said the "awkward" truth is that "often it requires a tragedy in this country for somebody to do something. At the end of the day you're talking about a child's life - or anybody's life - and even an injury is bad enough".
But he added: "To be fair to councils, they're having their funds cut right, left and centre, and they have to chop certain things especially if they don't have to do it".
Many local authorities use very basic testing equipment, which can be highly subjective, but some are now investing in the German-made microdrill, which Sorbus sells for around £7000.
The National Trust and "risk-averse" companies such as Center Parcs and tree adventure specialists Go Ape all use the device, and it is used worldwide to check utility poles are sound. Many play equipment manufacturers own the microdrill as do some consultants and contractors.
"With play equipment, once the decay sets into it there's only one way it can go - it can only ever get worse," said Wade. "But a tree can sometimes respond by putting reaction wood on. For example, most ancient oaks are hollow but it doesn't matter as they are not going to fall over because they produce extra wood to compensate for the fungus attack." Testing several times in sequence can show whether that process is occurring.
Resi-PD Microdrill used to test trees and timber play equipment
The electronic Resi-PD microdrill drives a steel needle into the wood at constant speed and measures the penetration resistance of the timber. Sorbus International director Phil Wade said other microdrills can give inaccurate results because the frictional drag on the needle can obscure the fact that it has in fact hit rot or a cavity. But the Resi-PD uses a dual recording system, with one motor that spins the needle while a second pushes it in and is not affected by drag, making it more sensitive and clearly showing decay or cavities.